{"id":"CVE-2026-86000","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-86000","summary":"Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.9, the selector parser in src/soupsieve/css_parser.py defines IDENTIFIER with adjacent quantified…","details":"Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.9, the selector parser in src/soupsieve/css_parser.py defines IDENTIFIER with adjacent quantified groups over overlapping character classes, and VALUE embeds IDENTIFIER for attribute selectors. When an attacker-controlled selector contains a long identifier or unquoted attribute-value run followed by input that makes the overall match fail, the regular expression engine explores quadratically many splits between the overlapping groups. User-controlled selectors can reach this path through soupsieve.compile(), soupsieve.select(), or BeautifulSoup.select(), while applications using only hard-coded selectors are unaffected. The resulting CPU consumption can hold the Python GIL, exhaust application workers, and stall a service; successful plain identifier matches are linear, and the issue does not cause memory corruption or code execution. The issue is fixed in version 2.9.","published":"2026-09-17T16:18:16.757","modified":"2026-09-17T16:18:16.757","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":{"url":"https://github.com/facelessuser/soupsieve/commit/ce44e4996e6632871c18cdd7a7fb641be8ef34ef","label":"facelessuser/soupsieve@ce44e49"},"references":[{"type":"WEB","url":"https://github.com/facelessuser/soupsieve/commit/ce44e4996e6632871c18cdd7a7fb641be8ef34ef"},{"type":"WEB","url":"https://github.com/facelessuser/soupsieve/releases/tag/2.9"},{"type":"WEB","url":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c"},{"type":"WEB","url":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-09-17T16:18:16.757"}}