{"cve":"CVE-2026-82397","nvd":{"published":"2026-08-31T22:17:22.920","modified":"2026-09-09T21:09:13.080","status":"Deferred","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400","CWE-1284"],"references":["https://github.com/tornadoweb/tornado/commit/8d6363ed7b69d5f0da806efe34d256627a2191de","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"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-82397","score":0.00346,"percentile":0.28188,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-mpf4-983q-p7j4","url":"https://osv.dev/vulnerability/GHSA-mpf4-983q-p7j4","summary":" Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop","modified":"2026-09-10T12:25:33.492830390Z","packages":[{"ecosystem":"PyPI","name":"tornado","purl":"pkg:pypi/tornado","ranges":["<6.5.8"],"fixed":["6.5.8"]}]},{"id":"PYSEC-2026-3928","url":"https://osv.dev/vulnerability/PYSEC-2026-3928","summary":" Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop","modified":"2026-09-10T12:15:15.559565535Z","packages":[{"ecosystem":"PyPI","name":"tornado","purl":"pkg:pypi/tornado","ranges":["<6.5.8"],"fixed":["6.5.8"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}