CVE-2026-49855

HIGH7.5

tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb)

Published Jul 14, 2026

Modified Yesterday

Details

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. This issue is fixed in version 6.5.6.

References

WEB

https://github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ff

WEB

https://github.com/tornadoweb/tornado/pull/3626

WEB

https://github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-49855

CVSS Analysis

CVSS v3.1

7.5