{"id":"CVE-2026-91991","summary":"Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs","details":"Tornado before 6.5.8 contains an incomplete fix for cookie attribute injection that allows attackers to inject arbitrary cookie attributes by passing capitalized or legacy keyword arguments to set_cookie. Attackers can embed semicolon-delimited data in capitalized parameters like Domain, Path, or SameSite to bypass validation and modify cookie security attributes.","aliases":["GHSA-wwv5-g3v4-889x"],"modified":"2026-09-17T03:47:20.957290082Z","published":"2026-09-15T15:18:32.408Z","database_specific":{"cwe_ids":["CWE-113"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91991.json","cna_assigner":"VulnCheck"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91991.json"},{"type":"ADVISORY","url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91991"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/tornado-before-6.5.8-cookie-attribute-injection-via-capitalized-kwargs"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/tornadoweb/tornado","events":[{"introduced":"7d6465056ceb7a054b3f64cf1c18271753b10482"},{"fixed":"a55abe3e3bf59994f29b2f7084c46341f0d4f6a7"}],"database_specific":{"extracted_events":[{"introduced":"6.5.5"},{"fixed":"6.5.8"},{"introduced":"0"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["v6.5.7","v6.5.6","v6.5.5"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-91991.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N"}]}