CVE-2025-67724

Tornado is a Python web framework and asynchronous networking library. In versions 6.5.2 and below, the supplied reason phrase is used unescaped in HTTP headers (where it could be used for header injection) or in HTML in the default error page (where it could be used for XSS) and can be exploited by passing untrusted or malicious data into the reason argument. Used by both RequestHandler.set_status and tornado.web.HTTPError, the argument is designed to allow applications to pass custom "reason" phrases (the "Not Found" in HTTP/1.1 404 Not Found) to the HTTP status line (mainly for non-standard status codes). This issue is fixed in version 6.5.3.

CVSS 3.1

6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

0.2% chance of exploitation in the next 30 days; higher than 14% of CVEs (scores of 2026-10-25)

CWEs

CWE-79, CWE-644

Published

2025-12-12

Modified

2026-10-07

Record from

the NVD, synced 2026-10-19

Affected

• tornadoweb:tornado

Packages (OSV)

References

• https://github.com/tornadoweb/tornado/commit/9c163aebeaad9e6e7d28bac1f33580eb00b0e421
• https://github.com/tornadoweb/tornado/releases/tag/v6.5.3
• https://github.com/tornadoweb/tornado/security/advisories/GHSA-pr2v-jx2c-wg9f

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