# CVE-2026-40575

> Vulnerability · severity: **CRITICAL** (CVSS 9.1).

## Description

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-regex` or `--skip-auth-route` is configured. An attacker can spoof this header so OAuth2 Proxy evaluates authentication and skip-auth rules against a different path than the one actually sent to the upstream application. This can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session. Impacted users are deployments that run oauth2-proxy with `--reverse-proxy` enabled and configure at least one `--skip-auth-regex` or `--skip-auth-route` rule. This issue is patched in `v7.15.2`. Some workarounds are available for those who cannot upgrade immediately. Strip any client-provided `X-Forwarded-Uri` header at the reverse proxy or load balancer level; explicitly overwrite `X-Forwarded-Uri` with the actual request URI before forwarding requests to OAuth2 Proxy; restrict direct client access to OAuth2 Proxy so it can only be reached through a trusted reverse proxy; and/or remove or narrow `--skip-auth-regex` / `--skip-auth-route` rules where possible. For nginx-based deployments, ensure `X-Forwarded-Uri` is set by nginx and not passed through from the client.

## Key facts

- **CVE ID:** CVE-2026-40575
- **Published:** 2026-04-22
- **CVSS severity:** CRITICAL
- **CVSS base score:** 9.1
- **CWE codes:** CWE-290

## Affected products

- `oauth2_proxy_project:oauth2_proxy`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40575

## Citation

> AI Analytics. CVE-2026-40575. Retrieved 2026-07-19 from https://api.ai-analytics.org/cve/CVE-2026-40575. Derived from NIST NVD. Licensed CC0.

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