{"id":"CVE-2026-86000","state":"PUBLISHED","title":"Soup Sieve: Polynomial-time ReDoS (O(n²)) in the `IDENTIFIER` / `VALUE` selector sub-patterns","description":"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.","publishedAt":"2026-09-17T15:21:57.724Z","updatedAt":"2026-09-17T15:45:49.251Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["facelessuser soupsieve"],"affected":[{"vendor":"facelessuser","product":"soupsieve","versions":[{"version":"< 2.9","status":"affected"}]}],"references":["https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c","https://github.com/facelessuser/soupsieve/commit/ce44e4996e6632871c18cdd7a7fb641be8ef34ef","https://github.com/facelessuser/soupsieve/releases/tag/2.9"],"weaknesses":["CWE-400","CWE-1333"],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/86xxx/CVE-2026-86000.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-86000","state":"PUBLISHED","datePublished":"2026-09-17T15:21:57.724Z","dateUpdated":"2026-09-17T15:45:49.251Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-09-04T19:17:36.246Z"},"containers":{"cna":{"title":"Soup Sieve: Polynomial-time ReDoS (O(n²)) in the `IDENTIFIER` / `VALUE` selector sub-patterns","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"facelessuser","product":"soupsieve","versions":[{"version":"< 2.9","status":"affected"}]}],"references":[{"url":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c","name":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/facelessuser/soupsieve/commit/ce44e4996e6632871c18cdd7a7fb641be8ef34ef","name":"https://github.com/facelessuser/soupsieve/commit/ce44e4996e6632871c18cdd7a7fb641be8ef34ef","tags":["x_refsource_MISC"]},{"url":"https://github.com/facelessuser/soupsieve/releases/tag/2.9","name":"https://github.com/facelessuser/soupsieve/releases/tag/2.9","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"CWE-400: Uncontrolled Resource Consumption","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1333","lang":"en","description":"CWE-1333: Inefficient Regular Expression Complexity","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-17T15:21:57.724Z"},"source":{"advisory":"GHSA-gjv8-xp57-g29c","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-gjv8-xp57-g29c","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-17T15:45:31.018009Z","id":"CVE-2026-86000","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-17T15:45:49.251Z"}}]}}}