Resource exhaustion in Tornado - CVE-2026-91990
Published: September 15, 2026 / Updated: September 16, 2026
Vulnerability identifier: #VU149938
CSH Severity: Medium
CVSS v4: 8.7 [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-ID: CVE-2026-91990
CWE-ID: CWE-400
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 uncontrolled resource consumption in the parse_multipart_form_data function in httputil.py when processing multipart/form-data requests. A remote attacker can send a multipart request containing numerous parts to cause a denial of service.
Affected software
Tornado
How to mitigate CVE-2026-91990
Install security update from vendor's website.
Tornado - update to 6.5.8