{"cve":"CVE-2026-85999","nvd":{"published":"2026-09-17T16:18:16.590","modified":"2026-09-23T18:12:04.247","status":"Awaiting Analysis","description":"Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.9, selector_iter in src/soupsieve/css_parser.py trims the raw selector with RE_WS_END, an end-anchored WSC whitespace-and-comment expression used with search(), so the regular expression engine retries a greedy scan at every starting offset. An attacker-controlled valid selector containing a long internal whitespace run, or a selector containing a long CSS comment run followed by another token, causes quadratic CPU work before tokenization. User-controlled selectors can reach the path through soupsieve.compile() and BeautifulSoup.select(), while applications using only hard-coded selectors are unaffected. This root cause is separate from the IDENTIFIER and VALUE backtracking vulnerability because the cost occurs in RE_WS_END.search during trimming rather than token matching. The resulting CPU consumption can hold the Python GIL, exhaust workers, and stall a service without causing memory corruption or code execution. The issue is fixed in version 2.9.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-400","CWE-1333"],"references":["https://github.com/facelessuser/soupsieve/commit/cf198fcddc9230f06ed39f974eba0ce076b85cda","https://github.com/facelessuser/soupsieve/releases/tag/2.9","https://github.com/facelessuser/soupsieve/security/advisories/GHSA-j934-xhv5-fg8f"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:55:23.253742848+00:00"},"epss":{"cve":"CVE-2026-85999","score":0.00609,"percentile":0.4917,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-j934-xhv5-fg8f","url":"https://osv.dev/vulnerability/GHSA-j934-xhv5-fg8f","summary":"Soup Sieve: Polynomial-time ReDoS (O(n²)) in the whitespace/comment trimming regex `RE_WS_END` (triggers on VALID selectors)","modified":"2026-10-01T17:56:03.541286563Z","packages":[{"ecosystem":"PyPI","name":"soupsieve","purl":"pkg:pypi/soupsieve","ranges":["<2.9.0"],"fixed":["2.9.0"]}]},{"id":"PYSEC-2026-4171","url":"https://osv.dev/vulnerability/PYSEC-2026-4171","summary":"Soup Sieve: Polynomial-time ReDoS (O(n²)) in the whitespace/comment trimming regex `RE_WS_END` (triggers on VALID selectors)","modified":"2026-10-01T17:45:16.845996024Z","packages":[{"ecosystem":"PyPI","name":"soupsieve","purl":"pkg:pypi/soupsieve","ranges":["<2.9.0"],"fixed":["2.9.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}