CVE-2026-91991CWE-113

CVE-2026-91991

Medium · published September 15, 2026

CVSS v3.1
5.4
EPSS
0%
Percentile
15.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.4 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS v4.0
6.3 · 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
EPSS
0.00247 · 15.1th percentile
Weakness
CWE-113 · Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
Published
2026-09-15T20:17Z
References (3)
https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x · [email protected]https://www.vulncheck.com/advisories/tornado-before-6.5.8-cookie-attribute-injection-via-capitalized-kwargs · [email protected]https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 17 SEP 03:33Z
    EPSS moved — → 0%
    epss
  • 15 SEP 15:18Z
    Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs
    cvelistv5