CVE-2026-49855

Name	CVE-2026-49855
Description	Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. 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-mgf9-4vpg-hj56
Fixed by: https://github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ff (v6.5.6)