{"id":"CVE-2026-86000","summary":"Soup Sieve: Polynomial-time ReDoS (O(n²)) in the `IDENTIFIER` / `VALUE` selector sub-patterns","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.","aliases":["GHSA-gjv8-xp57-g29c"],"modified":"2026-09-19T03:47:29.160610484Z","published":"2026-09-17T15:21:57.724Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-1333","CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86000.json"},"references":[{"type":"WEB","url":"https://github.com/facelessuser/soupsieve/releases/tag/2.9"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86000.json"},{"type":"ADVISORY","url":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86000"},{"type":"FIX","url":"https://github.com/facelessuser/soupsieve/commit/ce44e4996e6632871c18cdd7a7fb641be8ef34ef"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/facelessuser/soupsieve","events":[{"introduced":"0"},{"fixed":"ce44e4996e6632871c18cdd7a7fb641be8ef34ef"},{"fixed":"8763f914472fc83652babda708bed5c8ef287004"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"2.9"}]}}],"versions":["2.8.4","2.8.3","2.8.2","2.8.1","2.8","2.7","2.6","2.5","2.4.1","2.4","2.3.2.post1","2.3.2","2.3.1","2.3","2.2.1","2.2","2.1.0","2.0.1","2.0.0","1.9.4","1.9.3","1.9.2","1.9.1","1.9.0","1.8.0","1.7.3","1.7.2","1.7.1","1.7.0","1.6.1","1.6.0","1.5.0","1.4.0","1.3.1","1.3.0","1.2.1","1.2.0","1.1.0","1.0.2","1.0.1","1.0.0","1.0.0b2","1.0.0b1","0.6.0","0.5.3","0.5.2","0.5.1","0.5.0","0.4.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-86000.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}