Riskcovery

CVE-2026-68749

Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service

State
Published
Severity
8.2 High
Published
Aug 6, 2026
Updated
Aug 19, 2026
Reserved
Jul 31, 2026

Read the record on cve.org

Description

Inefficient Regular Expression Complexity vulnerability in the CSS scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to exhaust server CPU via a long CSS declaration in sanitized HTML. The declaration regex in HtmlSanitizeEx.Scrubber.CSS.scrub/1 matches the property name with an unbounded greedy [-\w]+ followed by a mandatory :, so a long run of word characters not followed by a colon makes the engine give back one character at a time and retry the colon at every start offset. The work is quadratic in the length of the run, and no length cap is applied to the CSS handed to the scrubber. An 80 KB <style> body costs roughly 2.4 seconds of scheduler time, so a few concurrent requests saturate the BEAM scheduler pool and make the application unresponsive.

The impact is CPU exhaustion only. Nothing is read, modified or disclosed.

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.

Scores

CVSSScoreVectorSource
4.08.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NEEF

Weaknesses

  • CWE-1333 Inefficient Regular Expression Complexity

Affected Products

ProductVersions
html_sanitize_exrrrene
  • 0.3.1 to before 1.4.5Affected
  • 1.5.0-rc.0 to before 1.5.3Affected
html_sanitize_exrrrene
  • 21f90012eb21aa36f4e3701b7547e12faf0f3c8b and laterAffectedfrom 4f4bd9eb254881462c0461fbab74b29188c2c133Not affectedfrom b673df33ddf982c8bd0a8bd6348aa247080b3b14Not affected

References

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