GHSA-9JXC-CWFW-GPG8
Vulnerability from github – Published: 2026-11-06 12:30 – Updated: 2026-11-06 12:30Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowlib allows an unauthenticated remote peer to exhaust the memory of an HTTP/2 endpoint via HPACK-indexed header fields.
cow_http2_machine:headers_decode/4 in src/cow_http2_machine.erl decodes every HEADERS block with cow_hpack:decode/3. It bounds the compressed block size and the number of fields, but not the size of the decoded header list that RFC 9113 section 6.5.2 places under SETTINGS_MAX_HEADER_LIST_SIZE. A peer stores one header value of up to the dynamic table size (4096 bytes by default) and then references it with one-byte indexed fields, so about 100 bytes on the wire decode to a header list of about 390 KB. A consumer that copies the decoded values, as Cowboy does when cowboy_http2:headers_to_map/2 joins repeated cookie fields into one binary, allocates that amount for every stream. The total across streams and connections is not bounded.
This issue affects cowlib: from 2.7.0 onward.
{
"affected": [],
"aliases": [
"CVE-2026-113431"
],
"database_specific": {
"cwe_ids": [
"CWE-770"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-11-06T11:17:04Z",
"severity": "HIGH"
},
"details": "Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowlib allows an unauthenticated remote peer to exhaust the memory of an HTTP/2 endpoint via HPACK-indexed header fields.\n\ncow_http2_machine:headers_decode/4 in src/cow_http2_machine.erl decodes every HEADERS block with cow_hpack:decode/3. It bounds the compressed block size and the number of fields, but not the size of the decoded header list that RFC 9113 section 6.5.2 places under SETTINGS_MAX_HEADER_LIST_SIZE. A peer stores one header value of up to the dynamic table size (4096 bytes by default) and then references it with one-byte indexed fields, so about 100 bytes on the wire decode to a header list of about 390 KB. A consumer that copies the decoded values, as Cowboy does when cowboy_http2:headers_to_map/2 joins repeated cookie fields into one binary, allocates that amount for every stream. The total across streams and connections is not bounded.\n\nThis issue affects cowlib: from 2.7.0 onward.",
"id": "GHSA-9jxc-cwfw-gpg8",
"modified": "2026-11-06T12:30:37Z",
"published": "2026-11-06T12:30:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113431"
},
{
"type": "WEB",
"url": "https://github.com/ninenines/cowlib/commit/a3b15e29b3067644bfd580246c87f7af7a90b3b8"
},
{
"type": "WEB",
"url": "https://github.com/ninenines/cowlib/commit/b461b119e78e4e09bb28b186b09da7ed4a86a0dd"
},
{
"type": "WEB",
"url": "https://cna.erlef.org/cves/CVE-2026-113431.html"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-113431"
}
],
"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/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"
}
]
}
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