CVE-2026-103261

NameCVE-2026-103261
DescriptionTornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs1149712

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
python-tornado (PTS)bookworm, bookworm (security)6.2.0-3+deb12u4vulnerable
trixie (security), trixie6.4.2-3+deb13u2vulnerable
forky, sid6.5.5-5vulnerable

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
python-tornadosource(unstable)(unfixed)1149712

Notes

https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65
Fixed by: https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93 (v6.5.9)
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