{"id":"CVE-2026-115927","aliases":[],"title":"Tornado: Event loop blocking and excess memory use from chunked bodies with many small chunks","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6.6.0.","severity":"medium","score":5.3,"published":"2026-10-26T19:37:40.584Z","modified":"2026-10-27T14:18:44.227Z","withdrawn":false,"knownExploited":false,"affected":[],"references":["https://github.com/tornadoweb/tornado/security/advisories/GHSA-r4j5-9xpp-3985","https://github.com/tornadoweb/tornado/pull/3773","https://github.com/tornadoweb/tornado/commit/ceab33581489751a66fba8566ad6d5960d4b01c8","https://github.com/tornadoweb/tornado/releases/tag/v6.6.0"],"sources":[{"name":"CVE","id":"CVE-2026-115927","modified":"2026-10-27T14:18:44.227Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-115927"}],"assessments":[{"source":"CNA","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3}]}