Tornadoweb Tornado up to 6.5.x Chunked Transfer Encoding resource consumption

Summaryinfo

A vulnerability described as problematic has been identified in Tornadoweb Tornado up to 6.5.x. This issue affects some unknown processing of the component Chunked Transfer Encoding. The manipulation results in resource consumption. This vulnerability is identified as CVE-2026-115927. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Tornadoweb Tornado up to 6.5.x. It has been classified as problematic. Affected is an unknown code block of the component Chunked Transfer Encoding. The manipulation with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. This is going to have an impact on availability. CVE summarizes:

Tornado is a Python web framework and asynchronous networking library. Prior to 6.6.0, Tornado decodes HTTP/1.1 chunked transfer encoding by processing body data that has already arrived without yielding to the event loop. A remote unauthenticated peer can send millions of one-byte chunks to monopolize the process event loop and stall every other connection served by that process, while lowering max_body_size only limits the duration of each request. For handlers that do not use @stream_request_body, retaining each chunk as a separate object can consume roughly twenty times the received body size, and SimpleAsyncHTTPClient has the same event-loop behavior when reading a response from a malicious server. This issue is fixed in version 6.6.0.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-115927 since 10/23/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 6.6.0 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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