Allocation of Resources Without Limits or Throttling in Tornado - CVE-2026-103261
Published: September 15, 2026 / Updated: October 1, 2026
Vulnerability identifier: #VU149940
CSH Severity: Medium
CVSS v4: 6.9 [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]
CVE-ID: CVE-2026-103261
CWE-ID: CWE-770
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to allocation of resources without limits in the HTTPServerRequest.__init__ query-string parsing path when processing a GET request with a query string containing thousands of fields. A remote attacker can send a specially crafted GET request with a high number of query-string fields to cause a denial of service.
Affected software
Tornado
How to mitigate CVE-2026-103261
Install security update from vendor's website.
Tornado - update to 6.5.9