{"id":"CVE-2026-91991","title":"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","summary":"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-de…","severity":"medium","cvss":5.4,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N","cwe":["CWE-113","CWE-915"],"vendor":"tornadoweb","product":"tornado","affected":["tornado >= 6.5.5 < 6.5.8"],"patched":["tornado 6.5.8"],"published":"2026-09-15","updated":"2026-09-21","sourceUpdated":"2026-09-21T20:17:39.740","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-91991","references":[{"url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/tornado-before-6.5.8-cookie-attribute-injection-via-capitalized-kwargs","label":"disclosure@vulncheck.com"},{"url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://github.com/tornadoweb/tornado/pull/3704"},{"url":"https://github.com/tornadoweb/tornado/pull/3706"},{"url":"https://github.com/tornadoweb/tornado/commit/6ef836e43e1278530041376adb32504daa977b91"},{"url":"https://github.com/tornadoweb/tornado/commit/da284767eae8e1f0484f123b8c3225f6465b09c7"},{"url":"https://github.com/tornadoweb/tornado"},{"url":"https://github.com/tornadoweb/tornado/releases/tag/v6.5.8"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-91991.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-91991"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2533964"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-91991"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91991"}],"tags":["nvd","cve.org","osv","pip","csaf","vex","red-hat","exploit-available"],"epss":0.00277,"epssPercentile":0.17936,"aliases":["GHSA-wwv5-g3v4-889x"],"ecosystem":"pip","exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-21T19:14:08.258516Z"},"ingestedAt":"2026-09-15T15:39:12.907Z","slug":"CVE-2026-91991","body":"## Overview\n\nTornado 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-91991)\n\nAffected packages:\n\n- `tornado >= 6.5.5, < 6.5.8`\n\nPatched in:\n\n- `tornado 6.5.8`\n\nSource: https://osv.dev/vulnerability/GHSA-wwv5-g3v4-889x\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Container Platform 4 · no fix planned: Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, … · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-91991.json)","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":29.7,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":208774,"id":"CVE-2026-91991","ts":1790020370746,"field":"exploit_available","old":"false","new":"true"}]}