CVE-2026-31958

Tornado has a DoS due to too many multipart parts

Published Mar 11, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4520-1 python-tornado security update
Github GHSA Github GHSA GHSA-qjxf-f2mg-c6mc Tornado is vulnerable to DoS due to too many multipart parts
Ubuntu USN Ubuntu USN USN-8198-1 Tornado vulnerabilities
Ubuntu USN Ubuntu USN USN-8198-2 Tornado vulnerabilities
History
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'}

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

Type Values Removed Values Added
Metrics ssvc

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

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Apr 1, 2026, 2:32 PM
Reserved
Mar 10, 2026, 3:40 PM
Status
Modified
Published
Mar 11, 2026, 8:16 PM
Modified
Jun 17, 2026, 10:34 AM
Severity
Moderate
Public date
Mar 11, 2026, 7:27 PM