Vulnerability in tornadoweb tornado

[ Why it matters ]Priority signals

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

[ Description ]Official description

Tornado before 6.4.1 ignores duplicate Transfer-Encoding: chunked headers, treating requests as having no message body and parsing the chunked body as a subsequent request. Attackers can exploit this inconsistency when Tornado is deployed behind proxies to perform HTTP request smuggling, enabling access control bypass, cache poisoning, or connection desynchronization.

[ 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-Bund19 Oct 2026WID-SEC-2026-4029

  Red Hat Enterprise Linux (python-tornado, resteasy-core, bubblewrap, pgvector): Multiple vulnerabilities Translated from German

  Risk highCVE-2026-89059CVE-2026-82397CVE-2026-87766+3 more CVEs

[ References ]References

• github.com/tornadoweb/tornado/security/advisories/GHSA-753j-mpmx-qq6gvendor-advisory
• www.vulncheck.com/advisories/tornado-before-6.4.1-http-request-smuggling-via-transfer-e…third-party-advisory