Vulnerability Description
Tornado 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/tornadoweb/tornado/commit/8d6363ed7b69d5f0da806efe34d256627a2
- https://github.com/tornadoweb/tornado/pull/3704
- https://github.com/tornadoweb/tornado/releases/tag/v6.5.8
- https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4
FAQ
What is CVE-2026-82397?
CVE-2026-82397 is a vulnerability with a CVSS score of 7.5 (HIGH). Tornado 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 w...
How severe is CVE-2026-82397?
CVE-2026-82397 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-82397?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.