{"schema_version":"1.7.5","id":"GHSA-qjxf-f2mg-c6mc","published":"2026-03-12T14:19:52Z","modified":"2026-06-08T20:00:14.385003861Z","aliases":["CVE-2026-31958","PYSEC-2026-140"],"related":["CGA-3jmv-9445-5g47"],"summary":"Tornado is vulnerable to DoS due to too many multipart parts","details":"In versions of Tornado prior to 6.5.5, the only limit on the number of parts in `multipart/form-data` is the `max_body_size` setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts. \n\nTornado 6.5.5 introduces new limits on the size and complexity of multipart bodies, including a default limit of 100 parts per request. These limits are configurable if needed; see `tornado.httputil.ParseMultipartConfig`. It is also now possible to disable `multipart/form-data` parsing entirely if it is not required for the application.","affected":[{"package":{"name":"tornado","ecosystem":"PyPI","purl":"pkg:pypi/tornado"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.5.5"}]}],"versions":["0.2","1.0","1.1","1.1.1","1.2","1.2.1","2.0","2.1","2.1.1","2.2","2.2.1","2.3","2.4","2.4.1","3.0","3.0.1","3.0.2","3.1","3.1.1","3.2","3.2.1","3.2.2","4.0","4.0.1","4.0.2","4.1","4.1b2","4.2","4.2.1","4.2b1","4.3","4.3b1","4.3b2","4.4","4.4.1","4.4.2","4.4.3","4.4b1","4.5","4.5.1","4.5.2","4.5.3","4.5b1","4.5b2","5.0","5.0.1","5.0.2","5.0a1","5.0b1","5.1","5.1.1","5.1b1","6.0","6.0.1","6.0.2","6.0.3","6.0.4","6.0a1","6.0b1","6.1","6.1b1","6.1b2","6.2","6.2b1","6.2b2","6.3","6.3.1","6.3.2","6.3.3","6.3b1","6.4","6.4.1","6.4.2","6.4b1","6.5","6.5.1","6.5.2","6.5.3","6.5.4","6.5b1"],"database_specific":{"last_known_affected_version_range":"<= 6.5.4","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-qjxf-f2mg-c6mc/GHSA-qjxf-f2mg-c6mc.json"}}],"references":[{"type":"WEB","url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-qjxf-f2mg-c6mc"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31958"},{"type":"WEB","url":"https://github.com/tornadoweb/tornado/commit/119a195e290c43ad2d63a2cf012c29d43d6ed839"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/tornado/PYSEC-2026-140.yaml"},{"type":"PACKAGE","url":"https://github.com/tornadoweb/tornado"},{"type":"WEB","url":"https://github.com/tornadoweb/tornado/releases/tag/v6.5.5"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2026/04/msg00000.html"}],"database_specific":{"cwe_ids":["CWE-400"],"github_reviewed":true,"github_reviewed_at":"2026-03-12T14:19:52Z","nvd_published_at":"2026-03-11T20:16:16Z","severity":"HIGH"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}