GHSA-684P-MHW3-3CWQ
Vulnerability from github – Published: 2026-08-06 18:30 – Updated: 2026-08-06 18:30Inefficient Algorithmic Complexity vulnerability in the traversal engine in rrrene html_sanitize_ex allows an unauthenticated remote attacker to exhaust server CPU and memory via a flat run of sibling elements in sanitized HTML. The list clause of HtmlSanitizeEx.Traverser.traverse/2 recurses on the tail of a sibling list and then evaluates List.flatten([head] ++ tail) over the already flattened result, so every one of n siblings copies and re-walks the entire remaining tail. The flattening is only needed for the rare case where scrub returns several replacement nodes for one node, but the cost is paid across the whole tail at every step, making traversal quadratic in sibling count.
The traverser sits on every public entry point, so no particular scrubber or configuration is required and the payload needs only allowed tags. A 160 KB body of 20,000 sibling elements occupies a scheduler for roughly 1.7 seconds, and the cost grows faster than the body does.
This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.
{
"affected": [],
"aliases": [
"CVE-2026-68750"
],
"database_specific": {
"cwe_ids": [
"CWE-407"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-06T16:16:51Z",
"severity": "HIGH"
},
"details": "Inefficient Algorithmic Complexity vulnerability in the traversal engine in rrrene html_sanitize_ex allows an unauthenticated remote attacker to exhaust server CPU and memory via a flat run of sibling elements in sanitized HTML. The list clause of HtmlSanitizeEx.Traverser.traverse/2 recurses on the tail of a sibling list and then evaluates List.flatten([head] ++ tail) over the already flattened result, so every one of n siblings copies and re-walks the entire remaining tail. The flattening is only needed for the rare case where scrub returns several replacement nodes for one node, but the cost is paid across the whole tail at every step, making traversal quadratic in sibling count.\n\nThe traverser sits on every public entry point, so no particular scrubber or configuration is required and the payload needs only allowed tags. A 160 KB body of 20,000 sibling elements occupies a scheduler for roughly 1.7 seconds, and the cost grows faster than the body does.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.",
"id": "GHSA-684p-mhw3-3cwq",
"modified": "2026-08-06T18:30:50Z",
"published": "2026-08-06T18:30:50Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-463q-p2fr-mh9p"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68750"
},
{
"type": "WEB",
"url": "https://github.com/rrrene/html_sanitize_ex/commit/9f5ccedbed230930813f992a1e6906fcf485981e"
},
{
"type": "WEB",
"url": "https://cna.erlef.org/cves/CVE-2026-68750.html"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-68750"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/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"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.