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.
History

Wed, 11 Mar 2026 19:45:00 +0000

Type Values Removed Values Added
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.
Title Tornado has a DoS due to too many multipart parts
Weaknesses CWE-400
References
Metrics cvssV4_0

{'score': 8.7, '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-11T19:27:23.380Z

Reserved: 2026-03-10T15:40:10.481Z

Link: CVE-2026-31958

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-03-11T20:16:16.617

Modified: 2026-03-11T20:16:16.617

Link: CVE-2026-31958

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.