CWE-400
DiscouragedUncontrolled Resource Consumption
Abstraction: Class · Status: Draft
The product does not properly control the allocation and maintenance of a limited resource.
6312 vulnerabilities reference this CWE, most recent first.
GHSA-93P9-8FJ5-VJV2
Vulnerability from github – Published: 2022-05-13 01:24 – Updated: 2022-05-13 01:24The sctp_auth_asoc_get_hmac function in net/sctp/auth.c in the Linux kernel before 2.6.36 does not properly validate the hmac_ids array of an SCTP peer, which allows remote attackers to cause a denial of service (memory corruption and panic) via a crafted value in the last element of this array.
{
"affected": [],
"aliases": [
"CVE-2010-3705"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2010-11-26T20:00:00Z",
"severity": "HIGH"
},
"details": "The sctp_auth_asoc_get_hmac function in net/sctp/auth.c in the Linux kernel before 2.6.36 does not properly validate the hmac_ids array of an SCTP peer, which allows remote attackers to cause a denial of service (memory corruption and panic) via a crafted value in the last element of this array.",
"id": "GHSA-93p9-8fj5-vjv2",
"modified": "2022-05-13T01:24:12Z",
"published": "2022-05-13T01:24:12Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2010-3705"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2010:0842"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2010:0958"
},
{
"type": "WEB",
"url": "https://access.redhat.com/security/cve/CVE-2010-3705"
},
{
"type": "WEB",
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=640036"
},
{
"type": "WEB",
"url": "http://git.kernel.org/?p=linux/kernel/git/davem/net-2.6.git%3Ba=commit%3Bh=51e97a12bef19b7e43199fc153cf9bd5f2140362"
},
{
"type": "WEB",
"url": "http://git.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commit;h=51e97a12bef19b7e43199fc153cf9bd5f2140362"
},
{
"type": "WEB",
"url": "http://lists.fedoraproject.org/pipermail/package-announce/2010-December/052513.html"
},
{
"type": "WEB",
"url": "http://marc.info/?l=linux-kernel\u0026m=128596992418814\u0026w=2"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/42745"
},
{
"type": "WEB",
"url": "http://www.debian.org/security/2010/dsa-2126"
},
{
"type": "WEB",
"url": "http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.36"
},
{
"type": "WEB",
"url": "http://www.mandriva.com/security/advisories?name=MDVSA-2011:029"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2010/10/04/2"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2010/10/04/7"
},
{
"type": "WEB",
"url": "http://www.redhat.com/support/errata/RHSA-2010-0842.html"
},
{
"type": "WEB",
"url": "http://www.redhat.com/support/errata/RHSA-2010-0958.html"
},
{
"type": "WEB",
"url": "http://www.ubuntu.com/usn/USN-1000-1"
},
{
"type": "WEB",
"url": "http://www.vupen.com/english/advisories/2010/3321"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-93PM-5P5F-3GHX
Vulnerability from github – Published: 2023-01-18 18:24 – Updated: 2023-10-23 19:18There is a denial of service vulnerability in the Content-Disposition parsing component of Rack. This vulnerability has been assigned the CVE identifier CVE-2022-44571.
Versions Affected: >= 2.0.0 Not affected: None. Fixed Versions: 2.0.9.2, 2.1.4.2, 2.2.6.1, 3.0.0.1 Impact
Carefully crafted input can cause Content-Disposition header parsing in Rack to take an unexpected amount of time, possibly resulting in a denial of service attack vector. This header is used typically used in multipart parsing. Any applications that parse multipart posts using Rack (virtually all Rails applications) are impacted. Releases
The fixed releases are available at the normal locations. Workarounds
There are no feasible workarounds for this issue. Patches
To aid users who aren’t able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.
2-0-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 2.0 series
2-1-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 2.1 series
2-2-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 2.2 series
3-0-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 3.0 series
{
"affected": [
{
"package": {
"ecosystem": "RubyGems",
"name": "rack"
},
"ranges": [
{
"events": [
{
"introduced": "2.0.0"
},
{
"fixed": "2.0.9.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "RubyGems",
"name": "rack"
},
"ranges": [
{
"events": [
{
"introduced": "2.1.0"
},
{
"fixed": "2.1.4.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "RubyGems",
"name": "rack"
},
"ranges": [
{
"events": [
{
"introduced": "2.2.0"
},
{
"fixed": "2.2.6.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "RubyGems",
"name": "rack"
},
"ranges": [
{
"events": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.0.4.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2022-44571"
],
"database_specific": {
"cwe_ids": [
"CWE-1333",
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2023-01-18T18:24:40Z",
"nvd_published_at": "2023-02-09T20:15:00Z",
"severity": "LOW"
},
"details": "There is a denial of service vulnerability in the Content-Disposition parsing component of Rack. This vulnerability has been assigned the CVE identifier CVE-2022-44571.\n\nVersions Affected: \u003e= 2.0.0 Not affected: None. Fixed Versions: 2.0.9.2, 2.1.4.2, 2.2.6.1, 3.0.0.1\nImpact\n\nCarefully crafted input can cause Content-Disposition header parsing in Rack to take an unexpected amount of time, possibly resulting in a denial of service attack vector. This header is used typically used in multipart parsing. Any applications that parse multipart posts using Rack (virtually all Rails applications) are impacted.\nReleases\n\nThe fixed releases are available at the normal locations.\nWorkarounds\n\nThere are no feasible workarounds for this issue.\nPatches\n\nTo aid users who aren\u2019t able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.\n\n 2-0-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 2.0 series\n 2-1-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 2.1 series\n 2-2-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 2.2 series\n 3-0-Fix-ReDoS-vulnerability-in-multipart-parser - Patch for 3.0 series\n",
"id": "GHSA-93pm-5p5f-3ghx",
"modified": "2023-10-23T19:18:08Z",
"published": "2023-01-18T18:24:40Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-44571"
},
{
"type": "WEB",
"url": "https://discuss.rubyonrails.org/t/cve-2022-44571-possible-denial-of-service-vulnerability-in-rack-content-disposition-parsing/82126"
},
{
"type": "PACKAGE",
"url": "https://github.com/rack/rack"
},
{
"type": "WEB",
"url": "https://github.com/rack/rack/releases/tag/v3.0.4.1"
},
{
"type": "WEB",
"url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2022-44571.yml"
},
{
"type": "WEB",
"url": "https://www.debian.org/security/2023/dsa-5530"
}
],
"schema_version": "1.4.0",
"severity": [],
"summary": "Denial of Service Vulnerability in Rack Content-Disposition parsing"
}
GHSA-93R5-FHX6-VMG9
Vulnerability from github – Published: 2026-09-08 21:00 – Updated: 2026-09-08 21:00Summary
xmldom's malformed-input error-recovery path has two quadratic-time (O(n²)) behaviors that a
single crafted input triggers together, so a tiny, highly compressible document (tens of KB) stalls
the Node.js event loop for multiple seconds. It is reachable from DOMParser.parseFromString under
default options — i.e. from unauthenticated, network-delivered XML — making this an unauthenticated
denial of service. One of the two behaviors, the normalize() adjacent-text merge, is additionally
reachable programmatically — via a plain normalize() call on a DOM built with adjacent text nodes,
independent of the parser — so its fix must live in normalize(), not only in a parser bound.
Details
Finding A — parseElementStartPart quadratic re-scan
A < character is not a delimiter in any tag-parsing state, so parseElementStartPart scans
forward character-by-character over any embedded < until it reaches the next > (or end of
input), then validates the accumulated slice as a tag name and throws invalid tagName: on failure.
The main loop catches this, reports an error, sets end = -1, and recovers by advancing a single
character (appendText(Math.max(tagStart, start) + 1)). With a long run of < and a distant >,
each of the O(n) recovery retries performs an O(n) scan plus an O(n) anchored regex validation over
the growing candidate ⇒ O(n²).
Code (0.9.x, bb7a085dc5ba1eea3212388509b97bb4b4af32b9):
parseElementStartPartcharacter scan — https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L263-L461- tag-name validation (
setTagName→ throwsinvalid tagName) — https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L886-L891 - main-loop
catch→error+end = -1— https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L234-L242 - single-character recovery fallback — https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L247
Code (0.8.x, e5c14802592685bb872c042c54c3f73758875c85):
parseElementStartPart— https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L227catch→error+end = -1— https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L202-L208- recovery fallback — https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L213
setTagNamevalidation — https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L616-L621
Finding B — normalize() adjacent-text O(K²) merge
endDocument() calls document.normalize(). For a parent with K adjacent text nodes (produced by
the one-character recovery of Finding A), normalize() performs K−1 merges. Each merge does a
removeChild — which re-indexes all child nodes of the parent (O(K)) — and an appendData —
which rebuilds the accumulator string this.data + text (O(K)). Total: O(K²).
Well-formed XML cannot produce adjacent text-node siblings through the parser (each text run is one
node; comments, CDATA, PIs, and elements sit between runs), so the parse-path trigger for Finding B
is the malformed-input recovery that emits single-character text nodes. The same O(K²) merge is,
however, independently reachable via the public normalize() API on a programmatically built tree
(see "Finding B is additionally reachable programmatically" below).
Code (0.9.x, bb7a085dc5ba1eea3212388509b97bb4b4af32b9):
endDocument→normalize()— https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom-parser.js#L418-L420normalize()adjacent-text merge — https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom.js#L1336-L1356removeChildre-index-all branch — https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom.js#L1788-L1798appendDatastring rebuild — https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom.js#L2786-L2790
Code (0.8.x, e5c14802592685bb872c042c54c3f73758875c85):
endDocument→normalize()— https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom-parser.js#L213-L214normalize()merge — https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom.js#L529-L549removeChildre-index-all branch — https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom.js#L756-L773appendDatastring rebuild — https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom.js#L1533
Finding B is additionally reachable programmatically (no parser involved)
Node.prototype.normalize() is public API on every Document/Element. A tree built entirely through
the ordinary DOM API — new DOMImplementation().createDocument(...), then K× createTextNode +
appendChild on one parent — reaches the same O(K²) merge when the application calls normalize(),
with no parsing and no error-recovery. The parser is only one of the two callers of the
vulnerable merge:
- the parser's automatic
endDocument()→document.normalize()(the parse-path trigger above), and - any explicit application call to the public
normalize()on a tree with adjacent text nodes.
XMLSerializer does not call normalize(), so serializing an un-merged tree is O(total text), not
O(K²); the O(K²) surface is exactly those two normalize() callers. Consequently a parser-side bound
alone cannot remediate Finding B — the fix must live in normalize().
Affected Versions
Both findings are present across the full published @xmldom/xmldom history — both
currently-maintained versions (0.8.x and 0.9.x) are affected — and across the retired unscoped
xmldom line. Finding B's normalize() merge is additionally reachable programmatically: a
direct normalize() call on a DOM built with adjacent text nodes hits the same O(K²) merge,
independent of the parser — so, unlike Finding A, it does not require the malformed-input recovery
path.
Proof of Concept
Default DOMParser, no options. The input is trivially compressible (a< / a<> repeated) and
never throws — it is parsed via the recovery path.
const { DOMParser } = require('@xmldom/xmldom');
// Silence the expected `error`-level recovery reports (default handler logs
// them to console.error without throwing; only fatalError throws).
console.error = function () {};
function timeParse(label, xml, mime) {
const t0 = process.hrtime.bigint();
new DOMParser().parseFromString(xml, mime); // completes; no exception
const ms = Number(process.hrtime.bigint() - t0) / 1e6;
console.log(label + ' bytes=' + Buffer.byteLength(xml) + ' time=' + ms.toFixed(1) + ' ms');
}
for (const N of [4000, 8000, 16000, 32000]) {
// Finding A: long re-scans, O(n^2) during parse.
timeParse('A N=' + N, '<r>' + 'a<'.repeat(N) + '</r>', 'text/xml');
// Finding B: short re-scans (cheap parse) but K adjacent text nodes -> O(K^2) in normalize().
timeParse('B N=' + N, '<r>' + 'a<>'.repeat(N) + '</r>', 'text/html');
// Combined: ONE input hits both A and B under the default parser.
timeParse('C N=' + N, '<r>' + 'a<'.repeat(N) + '</r>', 'text/xml');
}
Measured on Node v18.20.8 (absolute ms vary by host; the load-bearing fact is that doubling the input ~quadruples the time — canonical O(n²)):
Finding A, isolated ("<r>" + "a<"×N + "</r>", normalize disabled to isolate the re-scan):
| N | input bytes | @xmldom/xmldom 0.9.10 |
0.8.13 |
|---|---|---|---|
| 2000 | 4007 | 43 ms | 37 ms |
| 4000 | 8007 | 129 ms | 106 ms |
| 8000 | 16007 | 434 ms | 424 ms |
| 16000 | 32007 | 1629 ms | 1611 ms |
Finding B, isolated ("<r>" + "a<>"×N + "</r>", time attributable to normalize()):
| K (N) | input bytes | 0.9.10 | 0.8.13 |
|---|---|---|---|
| 4000 | 12007 | 120 ms | 165 ms |
| 8000 | 24007 | 589 ms | 771 ms |
| 16000 | 48007 | 3142 ms | 4448 ms |
| 32000 | 96007 | 12127 ms | 12951 ms |
Combined (default parser, both findings; "<r>" + "a<"×N + "</r>"):
| N | input bytes | 0.9.10 | 0.8.13 |
|---|---|---|---|
| 4000 | 8007 | 341 ms | 397 ms |
| 8000 | 16007 | 1894 ms | 1641 ms |
| 16000 | 32007 | 4398 ms | 7661 ms |
~32 KB of input → several seconds of single-threaded event-loop stall.
Finding B via the public normalize() API (no parser)
const { DOMImplementation } = require('@xmldom/xmldom');
function timeNormalize(K) {
const doc = new DOMImplementation().createDocument(null, 'r', null);
const el = doc.documentElement;
for (let i = 0; i < K; i++) el.appendChild(doc.createTextNode('x')); // K adjacent text nodes
const t0 = process.hrtime.bigint();
doc.normalize(); // O(K^2) merge — no parsing involved
const ms = Number(process.hrtime.bigint() - t0) / 1e6;
console.log('K=' + K + ' time=' + ms.toFixed(1) + ' ms');
}
for (const K of [2000, 4000, 8000, 16000, 32000]) timeNormalize(K);
Measured on Node v18.20.8 (doubling K ~quadruples the time — O(K²)):
| K | 0.9.10 | 0.8.13 |
|---|---|---|
| 2000 | 5.7 ms | 5.6 ms |
| 32000 | 1263 ms | 1704 ms |
This path is reachable by any application that builds a DOM from attacker-influenced data and calls
normalize(), entirely independent of DOMParser.
Impact
Availability only: a single parse of a small crafted document blocks the Node.js event loop for the
duration of the quadratic work (multiple seconds at tens of KB; larger inputs scale as O(n²)). No
memory blow-up beyond transient strings, no data exposure, no integrity impact. Because XML is
routinely accepted from untrusted sources and parsed with default options, one request can stall a
server. The payloads are highly compressible, so any endpoint accepting compressed XML faces
additional amplification. Finding B is additionally reachable via an explicit normalize() call on a
programmatically built DOM (see Proof of Concept), so applications that construct a document from attacker-influenced
data and normalize it are exposed even without parsing.
Severity note
The complexity is quadratic, not exponential, so a multi-second stall requires
tens-to-hundreds of KB of input. VA:H reflects that xmldom applies no input-size limit and the
path runs on default-options parsing, so a single unbounded parse can fully stall the event loop.
Fix Applied
Two independent, non-breaking fixes shipped together — each alone leaves the other's quadratic cost dominating the default parse.
Finding A — terminate the malformed tag-name scan at an embedded <, so error recovery is linear instead of O(n²). DOM output is unchanged; only the reported error-message text differs (error strings are not a semver contract).
Finding B — merge adjacent text nodes in normalize() in O(K) instead of O(K²), which also closes the same slowdown reachable programmatically through a direct normalize() call. Both ship on both maintained versions.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.8.14"
},
"package": {
"ecosystem": "npm",
"name": "@xmldom/xmldom"
},
"ranges": [
{
"events": [
{
"introduced": "0.7.0"
},
{
"fixed": "0.8.15"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.9.11"
},
"package": {
"ecosystem": "npm",
"name": "@xmldom/xmldom"
},
"ranges": [
{
"events": [
{
"introduced": "0.9.0"
},
{
"fixed": "0.9.12"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "xmldom"
},
"ranges": [
{
"events": [
{
"introduced": "0.3.0"
},
{
"last_affected": "0.6.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-83614"
],
"database_specific": {
"cwe_ids": [
"CWE-400",
"CWE-407"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-08T21:00:41Z",
"nvd_published_at": "2026-09-01T15:17:39Z",
"severity": "HIGH"
},
"details": "## Summary\n\n`xmldom`\u0027s malformed-input **error-recovery path** has two quadratic-time (O(n\u00b2)) behaviors that a\nsingle crafted input triggers together, so a tiny, highly compressible document (tens of KB) stalls\nthe Node.js event loop for multiple seconds. It is reachable from `DOMParser.parseFromString` under\n**default options** \u2014 i.e. from unauthenticated, network-delivered XML \u2014 making this an unauthenticated\ndenial of service. One of the two behaviors, the `normalize()` adjacent-text merge, is **additionally\nreachable programmatically** \u2014 via a plain `normalize()` call on a DOM built with adjacent text nodes,\nindependent of the parser \u2014 so its fix must live in `normalize()`, not only in a parser bound.\n\n## Details\n\n### Finding A \u2014 `parseElementStartPart` quadratic re-scan\n\nA `\u003c` character is not a delimiter in any tag-parsing state, so `parseElementStartPart` scans\nforward character-by-character over any embedded `\u003c` until it reaches the next `\u003e` (or end of\ninput), then validates the accumulated slice as a tag name and throws `invalid tagName:` on failure.\nThe main loop catches this, reports an `error`, sets `end = -1`, and recovers by advancing a single\ncharacter (`appendText(Math.max(tagStart, start) + 1)`). With a long run of `\u003c` and a distant `\u003e`,\neach of the O(n) recovery retries performs an O(n) scan plus an O(n) anchored regex validation over\nthe growing candidate \u21d2 **O(n\u00b2)**.\n\nCode (0.9.x, `bb7a085dc5ba1eea3212388509b97bb4b4af32b9`):\n\n- `parseElementStartPart` character scan \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L263-L461\n- tag-name validation (`setTagName` \u2192 throws `invalid tagName`) \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L886-L891\n- main-loop `catch` \u2192 `error` + `end = -1` \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L234-L242\n- single-character recovery fallback \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/sax.js#L247\n\nCode (0.8.x, `e5c14802592685bb872c042c54c3f73758875c85`):\n\n- `parseElementStartPart` \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L227\n- `catch` \u2192 `error` + `end = -1` \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L202-L208\n- recovery fallback \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L213\n- `setTagName` validation \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L616-L621\n\n### Finding B \u2014 `normalize()` adjacent-text O(K\u00b2) merge\n\n`endDocument()` calls `document.normalize()`. For a parent with K adjacent text nodes (produced by\nthe one-character recovery of Finding A), `normalize()` performs K\u22121 merges. Each merge does a\n`removeChild` \u2014 which re-indexes **all** child nodes of the parent (O(K)) \u2014 and an `appendData` \u2014\nwhich rebuilds the accumulator string `this.data + text` (O(K)). Total: **O(K\u00b2)**.\n\nWell-formed XML cannot produce adjacent text-node siblings *through the parser* (each text run is one\nnode; comments, CDATA, PIs, and elements sit between runs), so the **parse-path** trigger for Finding B\nis the malformed-input recovery that emits single-character text nodes. The same O(K\u00b2) merge is,\nhowever, independently reachable via the public `normalize()` API on a programmatically built tree\n(see \"Finding B is additionally reachable programmatically\" below).\n\nCode (0.9.x, `bb7a085dc5ba1eea3212388509b97bb4b4af32b9`):\n\n- `endDocument` \u2192 `normalize()` \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom-parser.js#L418-L420\n- `normalize()` adjacent-text merge \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom.js#L1336-L1356\n- `removeChild` re-index-all branch \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom.js#L1788-L1798\n- `appendData` string rebuild \u2014 https://github.com/xmldom/xmldom/blob/bb7a085dc5ba1eea3212388509b97bb4b4af32b9/lib/dom.js#L2786-L2790\n\nCode (0.8.x, `e5c14802592685bb872c042c54c3f73758875c85`):\n\n- `endDocument` \u2192 `normalize()` \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom-parser.js#L213-L214\n- `normalize()` merge \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom.js#L529-L549\n- `removeChild` re-index-all branch \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom.js#L756-L773\n- `appendData` string rebuild \u2014 https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/dom.js#L1533\n\n### Finding B is additionally reachable programmatically (no parser involved)\n\n`Node.prototype.normalize()` is public API on every `Document`/`Element`. A tree built entirely through\nthe ordinary DOM API \u2014 `new DOMImplementation().createDocument(...)`, then K\u00d7 `createTextNode` +\n`appendChild` on one parent \u2014 reaches the **same** O(K\u00b2) merge when the application calls `normalize()`,\nwith **no** parsing and **no** error-recovery. The parser is only *one* of the two callers of the\nvulnerable merge:\n\n- the parser\u0027s automatic `endDocument()` \u2192 `document.normalize()` (the parse-path trigger above), and\n- any explicit application call to the public `normalize()` on a tree with adjacent text nodes.\n\n`XMLSerializer` does **not** call `normalize()`, so serializing an un-merged tree is O(total text), not\nO(K\u00b2); the O(K\u00b2) surface is exactly those two `normalize()` callers. Consequently a parser-side bound\nalone cannot remediate Finding B \u2014 the fix must live in `normalize()`.\n\n## Affected Versions\n\nBoth findings are present across the full published `@xmldom/xmldom` history \u2014 both\ncurrently-maintained versions (`0.8.x` and `0.9.x`) are affected \u2014 and across the retired unscoped\n`xmldom` line. Finding B\u0027s `normalize()` merge is additionally reachable **programmatically**: a\ndirect `normalize()` call on a DOM built with adjacent text nodes hits the same O(K\u00b2) merge,\nindependent of the parser \u2014 so, unlike Finding A, it does not require the malformed-input recovery\npath.\n\n## Proof of Concept\n\nDefault `DOMParser`, no options. The input is trivially compressible (`a\u003c` / `a\u003c\u003e` repeated) and\nnever throws \u2014 it is parsed via the recovery path.\n\n```js\nconst { DOMParser } = require(\u0027@xmldom/xmldom\u0027);\n\n// Silence the expected `error`-level recovery reports (default handler logs\n// them to console.error without throwing; only fatalError throws).\nconsole.error = function () {};\n\nfunction timeParse(label, xml, mime) {\n const t0 = process.hrtime.bigint();\n new DOMParser().parseFromString(xml, mime); // completes; no exception\n const ms = Number(process.hrtime.bigint() - t0) / 1e6;\n console.log(label + \u0027 bytes=\u0027 + Buffer.byteLength(xml) + \u0027 time=\u0027 + ms.toFixed(1) + \u0027 ms\u0027);\n}\n\nfor (const N of [4000, 8000, 16000, 32000]) {\n // Finding A: long re-scans, O(n^2) during parse.\n timeParse(\u0027A N=\u0027 + N, \u0027\u003cr\u003e\u0027 + \u0027a\u003c\u0027.repeat(N) + \u0027\u003c/r\u003e\u0027, \u0027text/xml\u0027);\n // Finding B: short re-scans (cheap parse) but K adjacent text nodes -\u003e O(K^2) in normalize().\n timeParse(\u0027B N=\u0027 + N, \u0027\u003cr\u003e\u0027 + \u0027a\u003c\u003e\u0027.repeat(N) + \u0027\u003c/r\u003e\u0027, \u0027text/html\u0027);\n // Combined: ONE input hits both A and B under the default parser.\n timeParse(\u0027C N=\u0027 + N, \u0027\u003cr\u003e\u0027 + \u0027a\u003c\u0027.repeat(N) + \u0027\u003c/r\u003e\u0027, \u0027text/xml\u0027);\n}\n```\n\nMeasured on Node v18.20.8 (absolute ms vary by host; the load-bearing fact is that doubling the\ninput ~quadruples the time \u2014 canonical O(n\u00b2)):\n\nFinding A, isolated (`\"\u003cr\u003e\" + \"a\u003c\"\u00d7N + \"\u003c/r\u003e\"`, normalize disabled to isolate the re-scan):\n\n| N | input bytes | `@xmldom/xmldom` 0.9.10 | 0.8.13 |\n|--:|--:|--:|--:|\n| 2000 | 4007 | 43 ms | 37 ms |\n| 4000 | 8007 | 129 ms | 106 ms |\n| 8000 | 16007 | 434 ms | 424 ms |\n| 16000 | 32007 | 1629 ms | 1611 ms |\n\nFinding B, isolated (`\"\u003cr\u003e\" + \"a\u003c\u003e\"\u00d7N + \"\u003c/r\u003e\"`, time attributable to `normalize()`):\n\n| K (N) | input bytes | 0.9.10 | 0.8.13 |\n|--:|--:|--:|--:|\n| 4000 | 12007 | 120 ms | 165 ms |\n| 8000 | 24007 | 589 ms | 771 ms |\n| 16000 | 48007 | 3142 ms | 4448 ms |\n| 32000 | 96007 | 12127 ms | 12951 ms |\n\nCombined (default parser, both findings; `\"\u003cr\u003e\" + \"a\u003c\"\u00d7N + \"\u003c/r\u003e\"`):\n\n| N | input bytes | 0.9.10 | 0.8.13 |\n|--:|--:|--:|--:|\n| 4000 | 8007 | 341 ms | 397 ms |\n| 8000 | 16007 | 1894 ms | 1641 ms |\n| 16000 | 32007 | 4398 ms | 7661 ms |\n\n~32 KB of input \u2192 several seconds of single-threaded event-loop stall.\n\n### Finding B via the public `normalize()` API (no parser)\n\n```js\nconst { DOMImplementation } = require(\u0027@xmldom/xmldom\u0027);\n\nfunction timeNormalize(K) {\n const doc = new DOMImplementation().createDocument(null, \u0027r\u0027, null);\n const el = doc.documentElement;\n for (let i = 0; i \u003c K; i++) el.appendChild(doc.createTextNode(\u0027x\u0027)); // K adjacent text nodes\n const t0 = process.hrtime.bigint();\n doc.normalize(); // O(K^2) merge \u2014 no parsing involved\n const ms = Number(process.hrtime.bigint() - t0) / 1e6;\n console.log(\u0027K=\u0027 + K + \u0027 time=\u0027 + ms.toFixed(1) + \u0027 ms\u0027);\n}\nfor (const K of [2000, 4000, 8000, 16000, 32000]) timeNormalize(K);\n```\n\nMeasured on Node v18.20.8 (doubling K ~quadruples the time \u2014 O(K\u00b2)):\n\n| K | 0.9.10 | 0.8.13 |\n|--:|--:|--:|\n| 2000 | 5.7 ms | 5.6 ms |\n| 32000 | 1263 ms | 1704 ms |\n\nThis path is reachable by any application that builds a DOM from attacker-influenced data and calls\n`normalize()`, entirely independent of `DOMParser`.\n\n## Impact\n\nAvailability only: a single parse of a small crafted document blocks the Node.js event loop for the\nduration of the quadratic work (multiple seconds at tens of KB; larger inputs scale as O(n\u00b2)). No\nmemory blow-up beyond transient strings, no data exposure, no integrity impact. Because XML is\nroutinely accepted from untrusted sources and parsed with default options, one request can stall a\nserver. The payloads are highly compressible, so any endpoint accepting compressed XML faces\nadditional amplification. Finding B is additionally reachable via an explicit `normalize()` call on a\nprogrammatically built DOM (see Proof of Concept), so applications that construct a document from attacker-influenced\ndata and normalize it are exposed even without parsing.\n\n## Severity note\n\nThe complexity is **quadratic**, not exponential, so a multi-second stall requires\ntens-to-hundreds of KB of input. `VA:H` reflects that xmldom applies **no** input-size limit and the\npath runs on default-options parsing, so a single unbounded parse can fully stall the event loop.\n\n## Fix Applied\n\nTwo independent, non-breaking fixes shipped together \u2014 each alone leaves the other\u0027s quadratic cost dominating the default parse.\nFinding A \u2014 terminate the malformed tag-name scan at an embedded `\u003c`, so error recovery is linear instead of O(n\u00b2). DOM output is unchanged; only the reported error-message text differs (error strings are not a semver contract).\nFinding B \u2014 merge adjacent text nodes in `normalize()` in O(K) instead of O(K\u00b2), which also closes the same slowdown reachable programmatically through a direct `normalize()` call. Both ship on both maintained versions.",
"id": "GHSA-93r5-fhx6-vmg9",
"modified": "2026-09-08T21:00:41Z",
"published": "2026-09-08T21:00:41Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/security/advisories/GHSA-93r5-fhx6-vmg9"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-83614"
},
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/pull/1071"
},
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/pull/1072"
},
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/commit/0748720b620555f8c222782dcab575cf0cf403b4"
},
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/commit/f40ccb861eee0acbf5ee4feb9a34932e87b329c9"
},
{
"type": "PACKAGE",
"url": "https://github.com/xmldom/xmldom"
},
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/releases/tag/0.8.15"
},
{
"type": "WEB",
"url": "https://github.com/xmldom/xmldom/releases/tag/0.9.12"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "xmldom: Quadratic-time parsing via the malformed-input recovery path \u2014 `parseElementStartPart` re-scan and `normalize()` adjacent-text merge"
}
GHSA-93V6-CJ2C-8C8G
Vulnerability from github – Published: 2022-01-29 00:00 – Updated: 2022-04-20 00:01A denial of service vulnerability exists in the netserver recv_command functionality of reolink RLC-410W v3.0.0.136_20121102. A specially-crafted network request can lead to a reboot. An attacker can send a malicious packet to trigger this vulnerability.
{
"affected": [],
"aliases": [
"CVE-2022-21801"
],
"database_specific": {
"cwe_ids": [
"CWE-190",
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-01-28T20:15:00Z",
"severity": "HIGH"
},
"details": "A denial of service vulnerability exists in the netserver recv_command functionality of reolink RLC-410W v3.0.0.136_20121102. A specially-crafted network request can lead to a reboot. An attacker can send a malicious packet to trigger this vulnerability.",
"id": "GHSA-93v6-cj2c-8c8g",
"modified": "2022-04-20T00:01:45Z",
"published": "2022-01-29T00:00:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-21801"
},
{
"type": "WEB",
"url": "https://talosintelligence.com/vulnerability_reports/TALOS-2021-1450"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-93WV-JW9V-4972
Vulnerability from github – Published: 2026-07-31 16:51 – Updated: 2026-07-31 16:51Summary
A remote, unauthenticated peer can leak one direct ByteBuf per HTTP/2 DATA frame in
applications that enable HTTP/2 content decompression via DelegatingDecompressorFrameListener.
When a DATA frame is processed for a stream whose decompressor has already been closed,
Http2Decompressor.decompress(...) retains the frame buffer but never releases it on the error
path, so its reference count never returns to zero. Repeating this over a long-lived HTTP/2
connection exhausts direct memory and crashes the JVM with OutOfMemoryError — a denial of service.
Details
In codec-http2/src/main/java/io/netty/handler/codec/http2/DelegatingDecompressorFrameListener.java,
Http2Decompressor.decompress(...) does:
// around line 433
decompressor.writeInbound(data.retain());
The argument data.retain() is evaluated before writeInbound(...) executes, incrementing the
buffer's reference count (refCnt: 1 -> 2). The very first statement of
EmbeddedChannel.writeInbound(...) is ensureOpen() (EmbeddedChannel.java:360), which throws
ClosedChannelException when the decompressor's internal EmbeddedChannel has already been closed.
When that happens:
- the DATA payload has been retain()ed but never entered the pipeline, so the decoder's
finally { release() } never runs;
- the surrounding catch (Throwable t) block in decompress(...) (around line 451) does not
release the extra reference;
- the input buffer therefore can never reach refCnt 0, and its (typically direct) memory is leaked.
The decompressor channel is closed on a reachable path:
Http2Connection onStreamRemoved → Http2Decompressor.cleanup() →
EmbeddedChannel.finishAndReleaseAll()
(DelegatingDecompressorFrameListener.java:125-133 and 418-420).
A peer that sends DATA frames for a stream whose decompressor has already been cleaned up (e.g.
continuing to send DATA after END_STREAM / stream removal) thus leaks one direct ByteBuf per
frame.
Affected code: DelegatingDecompressorFrameListener.java, method Http2Decompressor.decompress(...)
— the decompressor.writeInbound(data.retain()) call (line ~433) and its catch (Throwable t)
block (line ~451), which lacks a data.release() rollback.
Suggested fix: track whether writeInbound succeeded and roll back the extra retain() only when
the data never entered the pipeline:
boolean writeSucceeded = false;
try {
decompressor.writeInbound(data.retain());
writeSucceeded = true; // pipeline now owns the release
if (endOfStream) {
decompressor.finish();
}
return 0;
} catch (Throwable t) {
if (!writeSucceeded) {
data.release(); // roll back the extra retain(); data never entered pipeline
}
if (t instanceof Http2Exception) {
throw (Http2Exception) t;
}
throw streamError(stream.id(), INTERNAL_ERROR, t, ...);
}
| Case | writeSucceeded | catch action | Reason |
|---|---|---|---|
ensureOpen() throws (this bug) |
false |
data.release() |
data never entered pipeline |
| handler throws internally | true |
no release | decoder finally already released |
finish() throws |
true |
no release | writeInbound already succeeded |
PoC
Reproduced against the official, unmodified netty-codec-http2-4.2.15.Final.jar from Maven Central,
using real netty classes and measuring ByteBuf.refCnt() directly (the leaking logic is not mocked).
Reproduction steps:
- Download the official artifacts and their dependencies from Maven Central (version
4.2.15.Final):netty-common,netty-buffer,netty-transport,netty-resolver,netty-handler,netty-codec-base,netty-codec,netty-codec-http,netty-codec-http2,netty-codec-compression. - Build a real
Http2Decompressorwrapping a real gzip decoderEmbeddedChannel(ZlibCodecFactory.newZlibDecoder(ZlibWrapper.GZIP)). - Close the internal decompressor channel (equivalent to the end state of
cleanup()/finishAndReleaseAll()). - Encode a real gzip
DATApayload withZlibCodecFactory.newZlibEncoder(GZIP)(refCnt = 1). - Call
decompress(...)on the closed channel. - Observe:
writeInbound(...)throwsClosedChannelExceptionat itsensureOpen()entry (EmbeddedChannel.java:360), reached fromDelegatingDecompressorFrameListener.java:433;data.refCnt()is now2. - Release once as the frame reader would;
refCntstays at1(release()returnsfalse) → leaked.
Observed reference-count trace:
gzipData initial refCnt = 1
decompress -> data.retain() -> refCnt = 2 (retain applied, never rolled back)
caller releases once -> refCnt = 1 (release() returns false; not deallocated)
=> buffer never reaches 0 -> direct memory leaked
Observed exception stack (confirms the leak point):
java.nio.channels.ClosedChannelException
at io.netty.channel.embedded.EmbeddedChannel.checkOpen(EmbeddedChannel.java:959)
at io.netty.channel.embedded.EmbeddedChannel.ensureOpen(EmbeddedChannel.java:979)
at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:360)
at io.netty.handler.codec.http2.DelegatingDecompressorFrameListener$Http2Decompressor
.decompress(DelegatingDecompressorFrameListener.java:433)
Two notes on the harness (they do not affect the leak mechanism):
- The internal channel is closed directly via close() rather than through cleanup(). The end
state is identical (channel closed → writeInbound throws at ensureOpen()); the bug depends on
"channel closed → retain not rolled back", not on how the channel was closed.
- In the isolated harness the rethrown StreamException's root cause shows as NullPointerException
because the harness does not initialise an Http2LocalFlowController (a secondary exception
reported during channel close). The leak is already sealed at the ClosedChannelException thrown
by writeInbound's ensureOpen() (line 360); in a real server with the flow controller
initialised, the triggering exception is the ClosedChannelException itself.
A complete self-contained PoC (Verify02DecompressLeak.java, ~150 lines, no test framework) plus the
exact javac / java commands can be attached on request.
Impact
- Vulnerability type: uncontrolled resource consumption / memory leak (CWE-401), leading to
denial of service. Each crafted
DATAframe leaks one (typically direct/off-heap)ByteBuf. - Who is impacted: any server (or client) that enables HTTP/2 content decompression by installing
DelegatingDecompressorFrameListenerin its HTTP/2 pipeline. - Attacker requirements: remote, unauthenticated. The attacker only needs to send HTTP/2
DATAframes for a stream whose decompressor has been cleaned up (e.g. continue sendingDATAafterEND_STREAM). No special server configuration beyond decompression being enabled. - Result: sustained triggering over a long-lived connection exhausts direct memory and crashes
the JVM with
OutOfMemoryError.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 4.2.15.Final"
},
"package": {
"ecosystem": "Maven",
"name": "io.netty:netty-codec-http2"
},
"ranges": [
{
"events": [
{
"introduced": "4.2.0"
},
{
"fixed": "4.2.16.Final"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 4.1.135.Final"
},
"package": {
"ecosystem": "Maven",
"name": "io.netty:netty-codec-http2"
},
"ranges": [
{
"events": [
{
"introduced": "4.1.0.Final"
},
{
"fixed": "4.1.136.Final"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-56819"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-31T16:51:50Z",
"nvd_published_at": "2026-07-21T23:17:52Z",
"severity": "HIGH"
},
"details": "### Summary\n\nA remote, unauthenticated peer can leak one direct `ByteBuf` per HTTP/2 `DATA` frame in\napplications that enable HTTP/2 content decompression via `DelegatingDecompressorFrameListener`.\nWhen a `DATA` frame is processed for a stream whose decompressor has already been closed,\n`Http2Decompressor.decompress(...)` retains the frame buffer but never releases it on the error\npath, so its reference count never returns to zero. Repeating this over a long-lived HTTP/2\nconnection exhausts direct memory and crashes the JVM with `OutOfMemoryError` \u2014 a denial of service.\n\n### Details\n\nIn `codec-http2/src/main/java/io/netty/handler/codec/http2/DelegatingDecompressorFrameListener.java`,\n`Http2Decompressor.decompress(...)` does:\n\n```java\n// around line 433\ndecompressor.writeInbound(data.retain());\n```\n\nThe argument `data.retain()` is evaluated **before** `writeInbound(...)` executes, incrementing the\nbuffer\u0027s reference count (`refCnt: 1 -\u003e 2`). The very first statement of\n`EmbeddedChannel.writeInbound(...)` is `ensureOpen()` (`EmbeddedChannel.java:360`), which throws\n`ClosedChannelException` when the decompressor\u0027s internal `EmbeddedChannel` has already been closed.\n\nWhen that happens:\n- the `DATA` payload has been `retain()`ed but never entered the pipeline, so the decoder\u0027s\n `finally { release() }` never runs;\n- the surrounding `catch (Throwable t)` block in `decompress(...)` (around line 451) does **not**\n release the extra reference;\n- the input buffer therefore can never reach refCnt 0, and its (typically direct) memory is leaked.\n\nThe decompressor channel is closed on a reachable path:\n`Http2Connection` `onStreamRemoved` \u2192 `Http2Decompressor.cleanup()` \u2192\n`EmbeddedChannel.finishAndReleaseAll()`\n(`DelegatingDecompressorFrameListener.java:125-133` and `418-420`).\n\nA peer that sends `DATA` frames for a stream whose decompressor has already been cleaned up (e.g.\ncontinuing to send `DATA` after `END_STREAM` / stream removal) thus leaks one direct `ByteBuf` per\nframe.\n\n**Affected code**: `DelegatingDecompressorFrameListener.java`, method `Http2Decompressor.decompress(...)`\n\u2014 the `decompressor.writeInbound(data.retain())` call (line ~433) and its `catch (Throwable t)`\nblock (line ~451), which lacks a `data.release()` rollback.\n\n**Suggested fix**: track whether `writeInbound` succeeded and roll back the extra `retain()` only when\nthe data never entered the pipeline:\n\n```java\nboolean writeSucceeded = false;\ntry {\n decompressor.writeInbound(data.retain());\n writeSucceeded = true; // pipeline now owns the release\n if (endOfStream) {\n decompressor.finish();\n }\n return 0;\n} catch (Throwable t) {\n if (!writeSucceeded) {\n data.release(); // roll back the extra retain(); data never entered pipeline\n }\n if (t instanceof Http2Exception) {\n throw (Http2Exception) t;\n }\n throw streamError(stream.id(), INTERNAL_ERROR, t, ...);\n}\n```\n\n| Case | writeSucceeded | catch action | Reason |\n|------|:---:|---|---|\n| `ensureOpen()` throws (this bug) | `false` | `data.release()` | data never entered pipeline |\n| handler throws internally | `true` | no release | decoder `finally` already released |\n| `finish()` throws | `true` | no release | `writeInbound` already succeeded |\n\n### PoC\n\nReproduced against the official, unmodified `netty-codec-http2-4.2.15.Final.jar` from Maven Central,\nusing real netty classes and measuring `ByteBuf.refCnt()` directly (the leaking logic is not mocked).\n\nReproduction steps:\n\n1. Download the official artifacts and their dependencies from Maven Central (version `4.2.15.Final`):\n `netty-common`, `netty-buffer`, `netty-transport`, `netty-resolver`, `netty-handler`,\n `netty-codec-base`, `netty-codec`, `netty-codec-http`, `netty-codec-http2`,\n `netty-codec-compression`.\n2. Build a real `Http2Decompressor` wrapping a real gzip decoder `EmbeddedChannel`\n (`ZlibCodecFactory.newZlibDecoder(ZlibWrapper.GZIP)`).\n3. Close the internal decompressor channel (equivalent to the end state of\n `cleanup()` / `finishAndReleaseAll()`).\n4. Encode a real gzip `DATA` payload with `ZlibCodecFactory.newZlibEncoder(GZIP)` (`refCnt = 1`).\n5. Call `decompress(...)` on the closed channel.\n6. Observe: `writeInbound(...)` throws `ClosedChannelException` at its `ensureOpen()` entry\n (`EmbeddedChannel.java:360`), reached from `DelegatingDecompressorFrameListener.java:433`;\n `data.refCnt()` is now `2`.\n7. Release once as the frame reader would; `refCnt` stays at `1` (`release()` returns `false`) \u2192 leaked.\n\nObserved reference-count trace:\n\n```\ngzipData initial refCnt = 1\ndecompress -\u003e data.retain() -\u003e refCnt = 2 (retain applied, never rolled back)\ncaller releases once -\u003e refCnt = 1 (release() returns false; not deallocated)\n=\u003e buffer never reaches 0 -\u003e direct memory leaked\n```\n\nObserved exception stack (confirms the leak point):\n\n```\njava.nio.channels.ClosedChannelException\n at io.netty.channel.embedded.EmbeddedChannel.checkOpen(EmbeddedChannel.java:959)\n at io.netty.channel.embedded.EmbeddedChannel.ensureOpen(EmbeddedChannel.java:979)\n at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:360)\n at io.netty.handler.codec.http2.DelegatingDecompressorFrameListener$Http2Decompressor\n .decompress(DelegatingDecompressorFrameListener.java:433)\n```\n\nTwo notes on the harness (they do not affect the leak mechanism):\n- The internal channel is closed directly via `close()` rather than through `cleanup()`. The end\n state is identical (channel closed \u2192 `writeInbound` throws at `ensureOpen()`); the bug depends on\n \"channel closed \u2192 retain not rolled back\", not on *how* the channel was closed.\n- In the isolated harness the rethrown `StreamException`\u0027s root cause shows as `NullPointerException`\n because the harness does not initialise an `Http2LocalFlowController` (a secondary exception\n reported during channel close). The leak is already sealed at the `ClosedChannelException` thrown\n by `writeInbound`\u0027s `ensureOpen()` (line 360); in a real server with the flow controller\n initialised, the triggering exception is the `ClosedChannelException` itself.\n\nA complete self-contained PoC (`Verify02DecompressLeak.java`, ~150 lines, no test framework) plus the\nexact `javac` / `java` commands can be attached on request.\n\n### Impact\n\n- **Vulnerability type**: uncontrolled resource consumption / memory leak (CWE-401), leading to\n denial of service. Each crafted `DATA` frame leaks one (typically direct/off-heap) `ByteBuf`.\n- **Who is impacted**: any server (or client) that enables HTTP/2 content decompression by installing\n `DelegatingDecompressorFrameListener` in its HTTP/2 pipeline.\n- **Attacker requirements**: remote, unauthenticated. The attacker only needs to send HTTP/2 `DATA`\n frames for a stream whose decompressor has been cleaned up (e.g. continue sending `DATA` after\n `END_STREAM`). No special server configuration beyond decompression being enabled.\n- **Result**: sustained triggering over a long-lived connection exhausts direct memory and crashes\n the JVM with `OutOfMemoryError`.",
"id": "GHSA-93wv-jw9v-4972",
"modified": "2026-07-31T16:51:50Z",
"published": "2026-07-31T16:51:50Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/netty/netty/security/advisories/GHSA-93wv-jw9v-4972"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56819"
},
{
"type": "WEB",
"url": "https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b"
},
{
"type": "WEB",
"url": "https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6"
},
{
"type": "PACKAGE",
"url": "https://github.com/netty/netty"
},
{
"type": "WEB",
"url": "https://github.com/netty/netty/releases/tag/netty-4.1.136.Final"
},
{
"type": "WEB",
"url": "https://github.com/netty/netty/releases/tag/netty-4.2.16.Final"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is already closed (Direct memory leak / OOM DoS)"
}
GHSA-93WW-VWHW-JWXM
Vulnerability from github – Published: 2025-12-16 21:30 – Updated: 2025-12-16 21:30On affected platforms running Arista EOS with OSPFv3 configured, a specially crafted packet can cause the OSFPv3 process to have high CPU utilization which may result in the OSFPv3 process being restarted. This may cause disruption in the OSFPv3 routes on the switch.
This issue was discovered internally by Arista and is not aware of any malicious uses of this issue in customer networks.
{
"affected": [],
"aliases": [
"CVE-2025-8872"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-12-16T20:15:49Z",
"severity": "HIGH"
},
"details": "On affected platforms running Arista EOS with OSPFv3 configured, a specially crafted packet can cause the OSFPv3 process to have high CPU utilization which may result in the OSFPv3 process being restarted. This may cause disruption in the OSFPv3 routes on the switch.\n\nThis issue was discovered internally by Arista and is not aware of any malicious uses of this issue in customer networks.",
"id": "GHSA-93ww-vwhw-jwxm",
"modified": "2025-12-16T21:30:55Z",
"published": "2025-12-16T21:30:55Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-8872"
},
{
"type": "WEB",
"url": "https://www.arista.com/en/support/advisories-notices/security-advisory/23115-security-advisory-0128"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-93XJ-8MRV-444M
Vulnerability from github – Published: 2021-02-08 19:41 – Updated: 2024-09-23 16:13Impact
A malicious server which responds with long series of \xa0 characters in the www-authenticate header may cause Denial of Service (CPU burn while parsing header) of the httplib2 client accessing said server.
Patches
Version 0.19.0 contains new implementation of auth headers parsing, using pyparsing library. https://github.com/httplib2/httplib2/pull/182
Workarounds
import httplib2
httplib2.USE_WWW_AUTH_STRICT_PARSING = True
Technical Details
The vulnerable regular expression is https://github.com/httplib2/httplib2/blob/595e248d0958c00e83cb28f136a2a54772772b50/python3/httplib2/init.py#L336-L338
The section before the equals sign contains multiple overlapping groups. Ignoring the optional part containing a comma, we have:
\s*[^ \t\r\n=]+\s*=
Since all three infinitely repeating groups accept the non-breaking space character \xa0, a long string of \xa0 causes catastrophic backtracking.
The complexity is cubic, so doubling the length of the malicious string of \xa0 makes processing take 8 times as long.
Reproduction Steps
Run a malicious server which responds with
www-authenticate: x \xa0\xa0\xa0\xa0x
but with many more \xa0 characters.
An example malicious python server is below:
from http.server import BaseHTTPRequestHandler, HTTPServer
def make_header_value(n_spaces):
repeat = "\xa0" * n_spaces
return f"x {repeat}x"
class Handler(BaseHTTPRequestHandler):
def do_GET(self):
self.log_request(401)
self.send_response_only(401) # Don't bother sending Server and Date
n_spaces = (
int(self.path[1:]) # Can GET e.g. /100 to test shorter sequences
if len(self.path) > 1 else
65512 # Max header line length 65536
)
value = make_header_value(n_spaces)
self.send_header("www-authenticate", value) # This header can actually be sent multiple times
self.end_headers()
if __name__ == "__main__":
HTTPServer(("", 1337), Handler).serve_forever()
Connect to the server with httplib2:
import httplib2
httplib2.Http(".cache").request("http://localhost:1337", "GET")
To benchmark performance with shorter strings, you can set the path to a number e.g. http://localhost:1337/1000
References
Thanks to Ben Caller (Doyensec) for finding vulnerability and discrete notification.
For more information
If you have any questions or comments about this advisory: * Open an issue in httplib2 * Email current maintainer at 2021-01
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "httplib2"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.19.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2021-21240"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2021-02-08T19:41:34Z",
"nvd_published_at": "2021-02-08T20:15:00Z",
"severity": "HIGH"
},
"details": "### Impact\nA malicious server which responds with long series of `\\xa0` characters in the `www-authenticate` header may cause Denial of Service (CPU burn while parsing header) of the httplib2 client accessing said server.\n\n### Patches\nVersion 0.19.0 contains new implementation of auth headers parsing, using pyparsing library.\nhttps://github.com/httplib2/httplib2/pull/182\n\n### Workarounds\n```py\nimport httplib2\nhttplib2.USE_WWW_AUTH_STRICT_PARSING = True\n```\n\n### Technical Details\n\nThe vulnerable regular expression is https://github.com/httplib2/httplib2/blob/595e248d0958c00e83cb28f136a2a54772772b50/python3/httplib2/__init__.py#L336-L338\n\nThe section before the equals sign contains multiple overlapping groups. Ignoring the optional part containing a comma, we have:\n\n \\s*[^ \\t\\r\\n=]+\\s*=\n\nSince all three infinitely repeating groups accept the non-breaking space character `\\xa0`, a long string of `\\xa0` causes catastrophic backtracking.\n\nThe complexity is cubic, so doubling the length of the malicious string of `\\xa0` makes processing take 8 times as long.\n\n### Reproduction Steps\n\nRun a malicious server which responds with\n\n www-authenticate: x \\xa0\\xa0\\xa0\\xa0x\n\nbut with many more `\\xa0` characters.\n\nAn example malicious python server is below:\n\n```py\nfrom http.server import BaseHTTPRequestHandler, HTTPServer\n\ndef make_header_value(n_spaces):\n repeat = \"\\xa0\" * n_spaces\n return f\"x {repeat}x\"\n\nclass Handler(BaseHTTPRequestHandler):\n def do_GET(self):\n self.log_request(401)\n self.send_response_only(401) # Don\u0027t bother sending Server and Date\n n_spaces = (\n int(self.path[1:]) # Can GET e.g. /100 to test shorter sequences\n if len(self.path) \u003e 1 else\n 65512 # Max header line length 65536\n )\n value = make_header_value(n_spaces)\n self.send_header(\"www-authenticate\", value) # This header can actually be sent multiple times\n self.end_headers()\n\nif __name__ == \"__main__\":\n HTTPServer((\"\", 1337), Handler).serve_forever()\n```\n\nConnect to the server with httplib2:\n\n```py\nimport httplib2\nhttplib2.Http(\".cache\").request(\"http://localhost:1337\", \"GET\")\n```\n\nTo benchmark performance with shorter strings, you can set the path to a number e.g. http://localhost:1337/1000\n\n\n### References\nThanks to [Ben Caller](https://github.com/b-c-ds) ([Doyensec](https://doyensec.com)) for finding vulnerability and discrete notification.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [httplib2](https://github.com/httplib2/httplib2/issues/new)\n* Email [current maintainer at 2021-01](mailto:temotor@gmail.com)",
"id": "GHSA-93xj-8mrv-444m",
"modified": "2024-09-23T16:13:16Z",
"published": "2021-02-08T19:41:59Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-21240"
},
{
"type": "WEB",
"url": "https://github.com/httplib2/httplib2/pull/182"
},
{
"type": "WEB",
"url": "https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc"
},
{
"type": "PACKAGE",
"url": "https://github.com/httplib2/httplib2"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/httplib2/PYSEC-2021-16.yaml"
},
{
"type": "WEB",
"url": "https://pypi.org/project/httplib2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P",
"type": "CVSS_V4"
}
],
"summary": "Regular Expression Denial of Service (REDoS) in httplib2"
}
GHSA-9442-GM4V-R222
Vulnerability from github – Published: 2024-06-20 15:31 – Updated: 2026-02-27 21:38A vulnerability was found in Undertow, where URL-encoded request paths can be mishandled during concurrent requests on the AJP listener. This issue arises because the same buffer is used to decode the paths for multiple requests simultaneously, leading to incorrect path information being processed. As a result, the server may attempt to access the wrong path, causing errors such as "404 Not Found" or other application failures. This flaw can potentially lead to a denial of service, as legitimate resources become inaccessible due to the path mix-up.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "io.undertow:undertow-core"
},
"ranges": [
{
"events": [
{
"introduced": "2.3.0.Alpha1"
},
{
"fixed": "2.3.14.Final"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Maven",
"name": "io.undertow:undertow-core"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.2.33.Final"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2024-6162"
],
"database_specific": {
"cwe_ids": [
"CWE-400",
"CWE-488"
],
"github_reviewed": true,
"github_reviewed_at": "2024-06-20T16:22:33Z",
"nvd_published_at": "2024-06-20T15:15:50Z",
"severity": "HIGH"
},
"details": "A vulnerability was found in Undertow, where URL-encoded request paths can be mishandled during concurrent requests on the AJP listener. This issue arises because the same buffer is used to decode the paths for multiple requests simultaneously, leading to incorrect path information being processed. As a result, the server may attempt to access the wrong path, causing errors such as \"404 Not Found\" or other application failures. This flaw can potentially lead to a denial of service, as legitimate resources become inaccessible due to the path mix-up.",
"id": "GHSA-9442-gm4v-r222",
"modified": "2026-02-27T21:38:27Z",
"published": "2024-06-20T15:31:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-6162"
},
{
"type": "WEB",
"url": "https://github.com/undertow-io/undertow/pull/1612"
},
{
"type": "WEB",
"url": "https://github.com/undertow-io/undertow/commit/90f202ada89b6d9883beed0f1fe10c99d470d9a8"
},
{
"type": "WEB",
"url": "https://github.com/undertow-io/undertow/commit/a28ac53076e2fa532266d25e0c0b1a01d0e9d2cf"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2024:1194"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2024:4386"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2024:4884"
},
{
"type": "WEB",
"url": "https://access.redhat.com/security/cve/CVE-2024-6162"
},
{
"type": "WEB",
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2293069"
},
{
"type": "PACKAGE",
"url": "https://github.com/undertow-io/undertow"
},
{
"type": "WEB",
"url": "https://github.com/undertow-io/undertow/releases/tag/2.2.33.Final"
},
{
"type": "WEB",
"url": "https://github.com/undertow-io/undertow/releases/tag/2.3.14.Final"
},
{
"type": "WEB",
"url": "https://issues.redhat.com/browse/JBEAP-26268"
},
{
"type": "WEB",
"url": "https://issues.redhat.com/browse/UNDERTOW-2334"
},
{
"type": "WEB",
"url": "https://security.netapp.com/advisory/ntap-20241129-0009"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Undertow\u0027s url-encoded request path information can be broken on ajp-listener"
}
GHSA-944F-9X4F-P6C5
Vulnerability from github – Published: 2022-01-12 00:01 – Updated: 2024-11-14 21:31Windows Hyper-V Denial of Service Vulnerability.
{
"affected": [],
"aliases": [
"CVE-2022-21847"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-01-11T21:15:00Z",
"severity": "MODERATE"
},
"details": "Windows Hyper-V Denial of Service Vulnerability.",
"id": "GHSA-944f-9x4f-p6c5",
"modified": "2024-11-14T21:31:43Z",
"published": "2022-01-12T00:01:06Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-21847"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-21847"
},
{
"type": "WEB",
"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2022-21847"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-9492-C6V8-VJ2H
Vulnerability from github – Published: 2026-06-02 21:30 – Updated: 2026-06-03 21:30Dräger Infinity M300 patient worn monitors with software version VG2.x and earlier contain a network-based denial of service vulnerability that allows attackers with access to the hospital or Infinity Network to repeatedly trigger device reboots until the device enters a fail state requiring manual restart. Attackers can exploit this vulnerability to cause loss of wireless network connectivity, temporary loss of patient monitoring, and interruption of alarm functionality until the device is manually recovered.
{
"affected": [],
"aliases": [
"CVE-2019-25724"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-02T20:16:23Z",
"severity": "HIGH"
},
"details": "Dr\u00e4ger Infinity M300 patient worn monitors with software version VG2.x and earlier contain a network-based denial of service vulnerability that allows attackers with access to the hospital or Infinity Network to repeatedly trigger device reboots until the device enters a fail state requiring manual restart. Attackers can exploit this vulnerability to cause loss of wireless network connectivity, temporary loss of patient monitoring, and interruption of alarm functionality until the device is manually recovered.",
"id": "GHSA-9492-c6v8-vj2h",
"modified": "2026-06-03T21:30:27Z",
"published": "2026-06-02T21:30:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-25724"
},
{
"type": "WEB",
"url": "https://static.draeger.com/security"
},
{
"type": "WEB",
"url": "https://static.draeger.com/security/download/2019-277-02-M300-VG2x-Security-Advisory.pdf"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/dr-ger-infinity-m300-vg2-x-network-based-denial-of-service"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
Mitigation
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
Mitigation
- Mitigation of resource exhaustion attacks requires that the target system either:
- The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
- The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- recognizes the attack and denies that user further access for a given amount of time, or
- uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Mitigation
Ensure that protocols have specific limits of scale placed on them.
Mitigation
Ensure that all failures in resource allocation place the system into a safe posture.
CAPEC-147: XML Ping of the Death
An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.
CAPEC-227: Sustained Client Engagement
An adversary attempts to deny legitimate users access to a resource by continually engaging a specific resource in an attempt to keep the resource tied up as long as possible. The adversary's primary goal is not to crash or flood the target, which would alert defenders; rather it is to repeatedly perform actions or abuse algorithmic flaws such that a given resource is tied up and not available to a legitimate user. By carefully crafting a requests that keep the resource engaged through what is seemingly benign requests, legitimate users are limited or completely denied access to the resource.
CAPEC-492: Regular Expression Exponential Blowup
An adversary may execute an attack on a program that uses a poor Regular Expression(Regex) implementation by choosing input that results in an extreme situation for the Regex. A typical extreme situation operates at exponential time compared to the input size. This is due to most implementations using a Nondeterministic Finite Automaton(NFA) state machine to be built by the Regex algorithm since NFA allows backtracking and thus more complex regular expressions.