Vulnerability in Tornadoweb Tornado
CVE-2026-123535
Tornado before 6.6 does not validate the max_age argument of RequestHandler.set_cookie (also called by set_signed_cookie, set_secure_cookie, and clear_cookie), allowing injection of additional Set-Cookie attributes. When an application passes attacker-influenced input as max_age, an attacker can embed attributes such as Domain, Path, or Secure to widen the cookie's scope to parent paths or other subdomains.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.2 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (6.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 6.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/tornadoweb/tornado/security/advisories/GHSA-c6v4-qj2h-f748 (vendor-advisory)
- www.vulncheck.com/advisories/tornado-before-6.6-cookie-attribute-injection-via-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-123535?
- CVE-2026-123535 is a medium-severity vulnerability in Tornadoweb Tornado, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 4.2/10. Published 2026-11-08.
- How severe is CVE-2026-123535?
- Medium severity. CVSS v3 base score is 4.2 out of 10.