{"id":"UBUNTU-CVE-2026-85999","details":"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.","modified":"2026-09-23T23:36:45Z","published":"2026-09-17T16:18:00Z","upstream":["CVE-2026-85999"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-85999"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-85999"},{"type":"REPORT","url":"https://github.com/facelessuser/soupsieve/security/advisories/GHSA-j934-xhv5-fg8f"},{"type":"REPORT","url":"https://github.com/facelessuser/soupsieve/commit/cf198fcddc9230f06ed39f974eba0ce076b85cda"},{"type":"REPORT","url":"https://github.com/facelessuser/soupsieve/releases/tag/2.9"}],"affected":[{"package":{"name":"soupsieve","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/soupsieve?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.9.2+dfsg-2ubuntu1","1.9.4+dfsg-1","1.9.5+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python-soupsieve","binary_version":"1.9.5+dfsg-1"},{"binary_version":"1.9.5+dfsg-1","binary_name":"python3-soupsieve"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85999.json"}},{"package":{"name":"soupsieve","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/soupsieve?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.1-2","2.3-1","2.3.1-1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.3.1-1","binary_name":"python3-soupsieve"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85999.json"}},{"package":{"name":"soupsieve","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/soupsieve?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.4.1-2","2.5-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-soupsieve","binary_version":"2.5-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85999.json"}},{"package":{"name":"soupsieve","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/soupsieve?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.7-2","2.8.1-1","2.8.3-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-soupsieve","binary_version":"2.8.3-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85999.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"},{"type":"Ubuntu","score":"medium"}]}