{"id":"CVE-2026-115927","summary":"Tornado: Event loop blocking and excess memory use from chunked bodies with many small chunks","details":"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.","aliases":["GHSA-r4j5-9xpp-3985"],"modified":"2026-11-11T10:47:30.116518329Z","published":"2026-10-26T19:37:40.584Z","related":["openSUSE-SU-2026:12440-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/115xxx/CVE-2026-115927.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-400","CWE-770"]},"references":[{"type":"WEB","url":"https://github.com/tornadoweb/tornado/releases/tag/v6.6.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/115xxx/CVE-2026-115927.json"},{"type":"ADVISORY","url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-r4j5-9xpp-3985"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-115927"},{"type":"FIX","url":"https://github.com/tornadoweb/tornado/commit/ceab33581489751a66fba8566ad6d5960d4b01c8"},{"type":"FIX","url":"https://github.com/tornadoweb/tornado/pull/3773"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/tornadoweb/tornado","events":[{"introduced":"0"},{"fixed":"e2b0f452bbf0e554c64e9d9ee922341c1c634d95"},{"fixed":"ceab33581489751a66fba8566ad6d5960d4b01c8"}],"database_specific":{"extracted_events":[{"range":[{"introduced":"0"},{"fixed":"6.6.0"}],"source":"AFFECTED_FIELD","strategy":"StringRangeExpression"},{"range":[{"fixed":"ceab33581489751a66fba8566ad6d5960d4b01c8"}],"source":"REFERENCES_COMMIT"},{"source":"REFERENCES_TAG","original_tag":"v6.6.0","range":[{"fixed":"e2b0f452bbf0e554c64e9d9ee922341c1c634d95"}]}]}}],"versions":["v6.6.0rc1","v6.6.0b1","v6.6.0a1","v6.5.0","v6.5.0b1","v6.4.1","v6.4.0","v6.4.0b1","v6.3.1","v6.3.0","v6.3.0b1","v6.2.0","v6.2.0b2","v6.2.0b1","v6.1.0","v6.1.0b2","v6.1.0b1","v6.0.0","v6.0.0b1","v5.1.0","v5.0.0","v4.5.0","v4.5.1","v4.4.1","v4.4.0","v4.4.0b1","v4.3.0","v4.3.0b2","v4.3.0b1","v4.2.0","v4.2.0b1","v4.1.0","v4.1.0b2","v4.1.0b1","v4.0.0","v4.0.0b3","v4.0.0b2","v4.0.0b1","v3.2.0","v3.2.0b2","v3.2.0b1","v3.1.0","v3.0.1","v3.0.0","v2.1.1","v2.3.0","v2.2.0","v2.1.0","v2.0.0","v1.2.0","v1.1.0","v1.0.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-115927.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}