CVE-2026-68749: Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service
Inefficient Regular Expression Complexity vulnerability in the CSS scrubber in rrrene htmlsanitizeex 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 htmlsanitizeex: from 0.3.1 before 1.5.3.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-68749?
CVE-2026-68749 has a risk rating of 32, indicating a high severity level.
How do I fix CVE-2026-68749?
To fix CVE-2026-68749, update the rrrene html_sanitize_ex library to the latest version that addresses this vulnerability.
Who is affected by CVE-2026-68749?
Any application using the rrrene html_sanitize_ex library is susceptible to CVE-2026-68749.
What type of attack does CVE-2026-68749 enable?
CVE-2026-68749 allows unauthenticated remote attackers to launch a CPU exhaustion denial of service attack.
What component of the rrrene html_sanitize_ex is vulnerable in CVE-2026-68749?
The vulnerability lies in the CSS scrubber component of the rrrene html_sanitize_ex library.