CVE-2026-91991

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.

CVSS 4.0

6.3CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

CVSS 3.1

5.4CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

EPSS

0.2% chance of exploitation in the next 30 days; higher than 15% of CVEs (scores of 2026-10-25)

CWE

CWE-113

Published

2026-09-15

Modified

2026-10-08

Record from

the NVD, synced 2026-10-19

Packages (OSV)

References

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x
• https://www.vulncheck.com/advisories/tornado-before-6.5.8-cookie-attribute-injection-via-capitalized-kwargs
• https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x

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