TornadoWeb Tornado up to 6.5 HTTP Header Parser allocation of resources

Summaryinfo

A vulnerability has been found in TornadoWeb Tornado up to 6.5 and classified as problematic. Affected by this issue is some unknown functionality of the component HTTP Header Parser. This manipulation causes allocation of resources. This vulnerability is registered as CVE-2026-116577. Remote exploitation of the attack is possible. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in TornadoWeb Tornado up to 6.5. It has been declared as problematic. Affected by this vulnerability is an unknown part of the component HTTP Header Parser. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. The summary by CVE is:

Tornado is a Python web framework and asynchronous networking library. Prior to 6.6, Tornado's HTTP header parser accepts obsolete line folding and repeatedly concatenates short continuation lines, causing quadratic CPU consumption on the IOLoop thread. An unauthenticated client can submit a header block containing many obsolete line-folding continuations before application code runs, blocking other connections served by the process. The cost grows with max_header_size, and only availability is affected. This issue is fixed in version 6.6.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-116577 since 10/26/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 6.6 eliminates this vulnerability.

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Productinfo

Vendor

• TornadoWeb

Name

• Tornado

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5

Website

• Product: https://github.com/tornadoweb/tornado/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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