CVE-2026-65655: Temporal UI Server may set OAuth credential cookies without Secure behind a TLS-terminating reverse proxy
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Temporal UI Serverto a version that resolves this vulnerability.Fixed in 2.53.2 - Configuration
When OAuth authentication is enabled, ensure Temporal UI Server derives the authentication-cookie Secure attribute from the configured browser-facing OAuth callback URL (not the reverse proxy-to-server connection) and applies the resulting Secure decision consistently to all authentication cookies.
Temporal UI Server authentication-cookie Secure attribute (derived from browser-facing OAuth callback URL) = Set Secure based on configured browser-facing OAuth callback URL and apply consistently to all authentication cookies - Configuration
To prevent the demonstrated credential-disclosure path, use one of: effective HSTS for the UI hostname, a blocking HTTPS-only warning, or TLS re-encryption between the TLS-terminating reverse proxy and the Temporal UI Server.
HSTS / HTTPS-only warning / TLS between proxy and Temporal UI Server HTTPS enforcement for UI hostname = Enable effective HSTS, use a blocking HTTPS-only warning, or ensure TLS re-encryption between the proxy and Temporal UI Server
Event History
Frequently Asked Questions
What is the risk level of CVE-2026-65655?
CVE-2026-65655 has a risk level of 41.
What is the main issue described in CVE-2026-65655?
CVE-2026-65655 describes an issue where OAuth credential cookies may be set without the Secure attribute when using a TLS-terminating reverse proxy.
What are the potential consequences of CVE-2026-65655?
The potential consequences of CVE-2026-65655 include the exposure of sensitive OAuth credentials due to unsecured cookies.
How can organizations mitigate the risk of CVE-2026-65655?
Organizations can mitigate the risk of CVE-2026-65655 by ensuring the use of HTTPS between the reverse proxy and the Temporal UI Server.
Which versions are affected by CVE-2026-65655?
CVE-2026-65655 affects versions of the Temporal UI Server where OAuth authentication is enabled and configured improperly with an HTTP connection.