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.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-qjxf-f2mg-c6mc Tornado is vulnerable to DoS due to too many multipart parts
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Mon, 16 Mar 2026 19:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Fri, 13 Mar 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-770
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

threat_severity

Moderate


Thu, 12 Mar 2026 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 12 Mar 2026 10:15:00 +0000

Type Values Removed Values Added
First Time appeared Tornadoweb
Tornadoweb tornado
Vendors & Products Tornadoweb
Tornadoweb tornado

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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-12T19:55:50.969Z

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

Link: CVE-2026-31958

cve-icon Vulnrichment

Updated: 2026-03-12T19:55:47.727Z

cve-icon NVD

Status : Analyzed

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

Modified: 2026-03-16T19:32:06.370

Link: CVE-2026-31958

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-03-11T19:27:23Z

Links: CVE-2026-31958 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-03-12T09:56:43Z

Weaknesses