CVE-2026-82397

NameCVE-2026-82397
DescriptionTornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses the body before handler dispatch through HTTPServerRequest._parse_body and parse_body_arguments in tornado/httputil.py, so an unauthenticated request body containing millions of separator-delimited fields can synchronously stall the single-threaded event loop and delay every connection. The body is bounded only by max_buffer_size, which defaults to 104857600 bytes. This issue is fixed in version 6.5.8.
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)

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, sid6.5.5-4vulnerable

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

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

Notes

https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4
Fixed by: https://github.com/tornadoweb/tornado/commit/8d6363ed7b69d5f0da806efe34d256627a2191de (v6.5.8)

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