CVE-2026-34457
OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode
- State
- Published
- Severity
- 9.1 Critical
- Published
- Apr 14, 2026
- Updated
- Apr 15, 2026
- Reserved
- Mar 27, 2026
Description
OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions prior to 7.15.2 contain a configuration-dependent authentication bypass in deployments where OAuth2 Proxy is used with an auth_request-style integration (such as nginx auth_request) and either --ping-user-agent is set or --gcp-healthchecks is enabled. In affected configurations, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check regardless of the requested path, allowing an unauthenticated remote attacker to bypass authentication and access protected upstream resources. Deployments that do not use auth_request-style subrequests or that do not enable --ping-user-agent/--gcp-healthchecks are not affected. This issue is fixed in 7.15.2.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | GitHub_M |
Weaknesses
- CWE-290 Authentication Bypass by Spoofing
Affected Products
| Product | Versions |
|---|---|
oauth2-proxyoauth2-proxy |
|
References
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