Vulnerability Description
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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/tornadoweb/tornado/commit/ceab33581489751a66fba8566ad6d5960d4
- https://github.com/tornadoweb/tornado/pull/3773
- https://github.com/tornadoweb/tornado/releases/tag/v6.6.0
- https://github.com/tornadoweb/tornado/security/advisories/GHSA-r4j5-9xpp-3985
FAQ
What is CVE-2026-115927?
CVE-2026-115927 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 yield...
How severe is CVE-2026-115927?
CVE-2026-115927 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-115927?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.