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Vulnerability · Published Aug 6, 2026 · Assigned by EEF

CVE-2026-68750Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaustion denial of service

High 8.2

In plain English

A high-severity security flaw in html_sanitize_ex from rrrene. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities).

Severity (CVSS 4.0)8.2High
Exploit odds (30 days)0.8%top 43.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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. 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 1.4.5 and from 1.5.0-rc.0 before 1.5.3.

Affected products (as reported)

VendorProductVersions
rrrene html_sanitize_ex 0.3.1 – before 1.4.51.5.0-rc.0 – before 1.5.3
rrrene html_sanitize_ex 69ea11d61525c470b39b6860d024770d5573ff1f – before *

Weakness: CWE-407 · Vector: 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

References