Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve contains a regular expression vulnerable to catastrophic backtracking when processing an attribute selector with an unterminated quoted value in soupsieve/css_parser.py, allowing an attacker who can supply untrusted CSS selector strings to soupsieve.compile() or Beautiful Soup .select() / .select_one() to cause CPU exhaustion and denial of service. This issue is fixed in version 2.8.4.
Fix
Patch, vendor advisory and mitigation references on NVD 3
- https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3 Patch
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 Exploit, Vendor Advisory
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 Exploit, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 7.5 · facelessuserNVD modified 2026-10-24 21:10
Affected (CPE criteria) 1
cpe:2.3:a:facelessuser:soup_sieve:*:*:*:*:*:beautiful_soup:*:*
References 4
- https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3 Patch
- https://github.com/facelessuser/soupsieve/releases/tag/2.8.4 Release Notes
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 Exploit, Vendor Advisory
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 Exploit, Vendor Advisory