CVE-2026-49854

Name	CVE-2026-49854
Description	Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, the optional native extension tornado.speedups implemented websocket_mask without validating that the mask argument is exactly four bytes, allowing the C function to read up to three bytes beyond the provided buffer when reached through Tornado XSRF token decoding with the native extension active. This issue is fixed in version 6.5.6.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
python-tornado (PTS)	bullseye	6.1.0-1	vulnerable
	bullseye (security)	6.1.0-1+deb11u4	vulnerable
	bookworm, bookworm (security)	6.2.0-3+deb12u4	vulnerable
	trixie (security), trixie	6.4.2-3+deb13u2	vulnerable
	forky, sid	6.5.5-4	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
python-tornado	source	(unstable)	(unfixed)

Notes

https://github.com/tornadoweb/tornado/security/advisories/GHSA-cx3h-4qpv-8hc9
Fixed by: https://github.com/tornadoweb/tornado/commit/96dc88c2a05705287856b2cd6b4b4034f9a6aaac (v6.5.6)