CVE-2026-65655

When OAuth authentication is enabled and browser-facing TLS terminates at a reverse proxy that forwards the callback to Temporal UI Server over HTTP, affected versions derive authentication-cookie Secure attributes from the proxy-to-server connection. Temporal UI Server can therefore issue access-token cookies, and refresh-token cookies when provided by the identity provider, without Secure even though the browser completed login over HTTPS. A victim who visits attacker-controlled content while a credential remains live may expose that credential only if the attacker can also steer traffic for the UI hostname, prevent the browser's HTTPS connection from succeeding, serve the hostname over HTTP, and read a later same-site plaintext request. A malicious website alone cannot read the cookie, and passive observation of a successful TLS connection is insufficient. Effective HSTS, a blocking HTTPS-only warning, or TLS re-encryption between the proxy and Temporal UI Server prevents the demonstrated disclosure path. A recovered credential may be replayed within the victim's assigned permissions. Refresh-token replay additionally depends on the identity provider's issuance, expiry, rotation, and reuse-detection behavior.