Vulnerability in tornadoweb tornado

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

[ 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-8423-8fgw-73vqvendor-advisory
• www.vulncheck.com/advisories/tornado-before-6.5.8-memory-amplification-dos-via-multipartthird-party-advisory