CVE-2025-67724

Tornado vulnerable to Header Injection and XSS via reason argument

Description

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.

Scores

Weaknesses (CWE)

• CWE-79
• CWE-644

Advisories

• GHSA-pr2v-jx2c-wg9f — Tornado vulnerable to Header Injection and XSS via reason argument
• PYSEC-2025-265 — 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

European references

• ENISA EUVD · EUVD-2025-203032
• GCVE · GCVE-0-2025-67724

CERT-FR advisories

• CERTFR-2026-AVI-1056 — Multiples vulnérabilités dans les produits Splunk · cert.ssi.gouv.fr
• CERTFR-2026-AVI-0901 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
• CERTFR-2026-AVI-0641 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr

Affected configurations (NVD CPE)

• cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:* < 6.5.3

Affected products

References

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

Sources