OAuth2-Proxy is an open-source tool that can act as either a standalone reverse proxy or a middleware component integrated into existing reverse proxy or load balancer setups. In versions 7.10.0 and below, oauth2-proxy deployments are vulnerable when using the skip_auth_routes configuration option with regex patterns. Attackers can bypass authentication by crafting URLs with query parameters that satisfy configured regex patterns, allowing unauthorized access to protected resources. The issue stems from skip_auth_routes matching against the full request URI. Deployments using skip_auth_routes with regex patterns containing wildcards or broad matching patterns are most at risk. This issue is fixed in version 7.11.0. Workarounds include: auditing all skip_auth_routes configurations for overly permissive patterns, replacing wildcard patterns with exact path matches where possible, ensuring regex patterns are properly anchored (starting with ^ and ending with $), or implementing custom validation that strips query parameters before regex matching.

Affected: Go: github.com/oauth2-proxy/oauth2-proxy/v7

### Impact This vulnerability affects oauth2-proxy deployments using the `skip_auth_routes` configuration option with regex patterns. The vulnerability allows attackers to bypass authentication by crafting URLs with query parameters that satisfy the configured regex patterns, potentially gaining unauthorized access to protected resources.

The issue stems from `skip_auth_routes` matching against the full request URI (path + query parameters) instead of just the path as documented. This discrepancy enables authentication bypass attacks where attackers append malicious query parameters to access protected endpoints.

Example Attack:

* Configuration: `skip_auth_routes = [ "^/foo/.*/bar$" ]` * Intended behavior: Allow `/foo/something/bar` * Actual vulnerability: Also allows `/foo/critical_endpoint?param=/bar`

Deployments using `skip_auth_routes` with regex patterns containing wildcards or broad matching patterns are most at risk, especially when backend services ignore unknown query parameters.

### Patches A patch has been released with version [v7.11.0](https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.11.0).

### Workarounds

Immediate mitigations:

1. Review regex patterns: Audit all `skip_auth_routes` configurations for overly permissive patterns 2. Use precise patterns: Replace wildcard patterns with exact path matches where possible 3. Anchor patterns: Ensure regex patterns are properly anchored (start with `^` and end with `$`) 4. Path-only matching: Consid…

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