{"cve":"CVE-2026-31958","nvd":{"published":"2026-03-11T20:16:16.617","modified":"2026-06-17T10:34:50.473","status":"Modified","description":"Tornado is a Python web framework and asynchronous networking library. 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. This vulnerability is fixed in 6.5.5.","cvss_v4":{"vector":"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","score":8.7},"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"],"references":["https://github.com/tornadoweb/tornado/security/advisories/GHSA-qjxf-f2mg-c6mc","https://lists.debian.org/debian-lts-announce/2026/04/msg00000.html"],"products":["tornadoweb:tornado"],"source":"nvd","synced_at":"2026-10-19T22:25:53.701907451+00:00"},"epss":{"cve":"CVE-2026-31958","score":0.0039,"percentile":0.33112,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-qjxf-f2mg-c6mc","url":"https://osv.dev/vulnerability/GHSA-qjxf-f2mg-c6mc","summary":"Tornado is vulnerable to DoS due to too many multipart parts","modified":"2026-09-10T03:50:40.522968763Z","packages":[{"ecosystem":"PyPI","name":"tornado","purl":"pkg:pypi/tornado","ranges":["<6.5.5"],"fixed":["6.5.5"]}]},{"id":"PYSEC-2026-140","url":"https://osv.dev/vulnerability/PYSEC-2026-140","summary":"","modified":"2026-05-20T09:19:20.297525Z","packages":[{"ecosystem":"PyPI","name":"tornado","purl":"pkg:pypi/tornado","ranges":["<6.5.5"],"fixed":["6.5.5"]}]}],"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."]}