CVE-2026-34457

Workarounds

Users can mitigate this issue by:

• disabling --gcp-healthchecks
• removing any configured --ping-user-agent
• ensuring the reverse proxy does not forward client-controlled User-Agent headers to the OAuth2 Proxy auth subrequest
• using path-based health checks only, on dedicated health check endpoints

Example nginx mitigation for the auth subrequest:

location = /oauth2/auth {
    internal;
    proxy_pass http://127.0.0.1:4180;
    proxy_pass_request_body off;
    proxy_set_header Content-Length "";
    proxy_set_header Host $host;
    # set to value that isn't the same as your configured PingUserAgent or GCPs "GoogleHC/1.0"
    proxy_set_header User-Agent "oauth2-proxy-auth-request";
}

A configuration-dependent authentication bypass exists in OAuth2 Proxy.

Deployments are affected when all of the following are true:

• OAuth2 Proxy is used with an auth_request-style integration (for example, nginx auth_request)
• --ping-user-agent is set or --gcp-healthchecks is enabled

In affected configurations, OAuth2 Proxy will treat a request with the configured health check User-Agent value as a successful health check regardless of the requested path. This allows an unauthenticated remote attacker to bypass authentication and access protected upstream resources without completing the normal login flow.

This issue does not affect deployments that do not use auth_request-style subrequests, or that do not enable --ping-user-agent/--gcp-healthchecks.

CVE-2026-34457 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (7.15.2); upgrading removes the vulnerable code path.

Kodem intelligence

Users should upgrade to v7.15.2 or later once available. Deployments running versions prior to v7.15.2 should be considered affected if they use auth_request-style authentication together with --ping-user-agent or --gcp-healthchecks.

1. What is CVE-2026-34457? CVE-2026-34457 is a critical-severity security vulnerability in github.com/oauth2-proxy/oauth2-proxy/v7 (go), affecting versions < 7.15.2. It is fixed in 7.15.2.
2. How severe is CVE-2026-34457? CVE-2026-34457 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2026-34457?
   • github.com/oauth2-proxy/oauth2-proxy/v7 (go) (versions < 7.15.2)
   • github.com/oauth2-proxy/oauth2-proxy (go) (versions <= 3.2.0)
4. Is there a fix for CVE-2026-34457? Yes. CVE-2026-34457 is fixed in 7.15.2. Upgrade to this version or later.
5. Is CVE-2026-34457 exploitable, and should I be worried? Whether CVE-2026-34457 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34457 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34457? Upgrade github.com/oauth2-proxy/oauth2-proxy/v7 to 7.15.2 or later.