CVE-2026-68749 Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service
An unauthenticated attacker can cause CPU exhaustion and application unresponsiveness by submitting long CSS declarations to the html_sanitize_ex library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68749?
CVE-2026-68749 is a high-severity denial of service vulnerability in rrrene html_sanitize_ex, published on 6 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-68749?
1 open source package ship an affected version, including html_sanitize_ex. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
html_sanitize_ex Hex | From 0.3.1 | 1.4.5, 1.5.3 |
Products include Rrrene Htmlsanitizeex.
How do I fix CVE-2026-68749?
Upgrade html_sanitize_ex to a fixed version for your release line: 1.4.5 or 1.5.3.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-68749 being exploited?
There is no known exploitation of CVE-2026-68749 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in rrrene html_sanitize_ex
- CVE-2026-68750 Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaustion denial of service
- CVE-2026-66370 html_sanitize_ex HTML5 scrubber keeps attacker-supplied form-association attributes, allowing form hijacking
- CVE-2026-66829 html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection
- CVE-2026-66843 html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embedding
- CVE-2026-68747 CSS sanitizer allowlist bypass in html_sanitize_ex via non-declaration input
Sources
Also known as EEF-CVE-2026-68749, GHSA-4cx2-987x-rr2x, GHSA-8rjf-8hw9-j63g.