Vulnerability in tornadoweb tornado

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund11 Oct 2026WID-SEC-2026-3870

  Red Hat Enterprise Linux (python-tornado): Multiple vulnerabilities Translated from German

  CVE-2026-91990CVE-2026-49855CVE-2026-49853

[ References ]References

• github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56x_refsource_CONFIRM
• github.com/tornadoweb/tornado/pull/3626x_refsource_MISC
• github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ffx_refsource_MISC