CVE-2026-34454: OAuth2 Proxy: Session cookie not cleared when rendering sign-in page
Impact A regression introduced in v7.11.0 is preventing OAuth2 Proxy from clearing the session cookie when rendering the sign-in page.
This only impacts deployments that rely on the sign-in page as part of their logout flow. In those setups, a user may be shown the sign-in page while the existing session cookie remains valid, so the browser session is not actually logged out. On shared workstations be it browsers or devices, a subsequent user could continue to use the previous user's authenticated session.
Deployments that use a dedicated logout/sign-out endpoint to terminate sessions are not affected.
Patches This issue is fixed in v7.15.2.
Workarounds Do not rely on the sign-in page to clear an existing session. Instead:
- Use the dedicated logout/sign-out endpoint of OAuth2 Proxy - Ensure your application logout flow explicitly clears the OAuth2 Proxy session cookie before redirecting users to the sign-in page - If needed, clear the session cookie at the reverse proxy or application layer as a temporary mitigation
Other sources
OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. A regression introduced in 7.11.0 prevents OAuth2 Proxy from clearing the session cookie when rendering the sign-in page. In deployments that rely on the sign-in page as part of their logout flow, a user may be shown the sign-in page while the existing session cookie remains valid, meaning the browser session is not actually logged out. On shared workstations or devices, a subsequent user could continue to use the previous user's authenticated session. Deployments that use a dedicated logout/sign-out endpoint to terminate sessions are not affected. This issue is fixed in 7.15.2
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/oauth2-proxy/oauth2-proxy/v7to a version that resolves this vulnerability.Fixed in 7.15.2 - Upgrade
Upgrade
oauth2-proxyto a version that resolves this vulnerability.Fixed in 7.15.2 - Configuration
In application logout flow, ensure the OAuth2 Proxy session cookie is explicitly cleared before redirecting users to the sign-in page. If needed as a temporary mitigation, clear the session cookie at the reverse proxy or application layer, and use OAuth2 Proxy’s dedicated logout/sign-out endpoint to terminate sessions.
OAuth2 Proxy logout flow (session cookie clearing) = explicitly clear OAuth2 Proxy session cookie before redirecting to sign-in page; use dedicated logout/sign-out endpoint
Event History
Frequently Asked Questions
What is the severity of CVE-2026-34454?
CVE-2026-34454 is categorized as a medium severity vulnerability due to improper handling of session cookies.
How do I fix CVE-2026-34454?
To mitigate CVE-2026-34454, upgrade OAuth2 Proxy to version 7.15.2 or later.
What versions of OAuth2 Proxy are affected by CVE-2026-34454?
CVE-2026-34454 affects OAuth2 Proxy versions from 7.11.0 to 7.15.2.
What impact does CVE-2026-34454 have on my application?
CVE-2026-34454 may leave session cookies uncleared, potentially allowing unauthorized access to user sessions.
When was CVE-2026-34454 reported?
CVE-2026-34454 was reported following a regression introduced in OAuth2 Proxy version 7.11.0.