Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.
Advisories

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Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 01 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Thu, 01 Oct 2026 11:00:00 +0000

Type Values Removed Values Added
Description Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.
Title Tornado before 6.5.9 Denial of Service via Query String
First Time appeared Tornadoweb
Tornadoweb tornado
Weaknesses CWE-770
CPEs cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:*
Vendors & Products Tornadoweb
Tornadoweb tornado
References
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'}

cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-01T14:44:26.683Z

Reserved: 2026-09-30T10:55:39.869Z

Link: CVE-2026-103261

cve-icon Vulnrichment

Updated: 2026-10-01T14:44:19.859Z

cve-icon NVD

Status : Deferred

Published: 2026-10-01T11:17:20.847

Modified: 2026-10-01T15:17:26.580

Link: CVE-2026-103261

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-01T14:15:09Z

Weaknesses