[ CVE-2026-116578 · Published 26 Oct 2026 ]

Tornado: Open redirect in RedirectHandler via protocol-relative URLs

CVSS 2.1 EPSS <1%Fix available

[ Description ]Official description

Tornado is a Python web framework and asynchronous networking library. Prior to 6.6, tornado.web.RedirectHandler URL templates can place regex-capture substitutions where crafted request paths change the redirect scheme or network location. Affected placements include substitutions at the start of a path, directly after a fixed host, or at the beginning of the template, including protocol-relative, absolute, backslash, encoded, host-extension, and user-info variants interpreted by browsers as attacker-controlled destinations. Static templates and substitutions after a fixed host followed by a slash are not affected. An attacker can use the resulting open redirect on the application's domain for phishing. This issue is fixed in version 6.6.

[ Fixes ]Fixes and patches

  • tornado 6.6Fixed version · GitHub Advisories · pip package tornado: upgrade to 6.6 or later (affected < 6.6)

[ Packages ]Affected open-source packages