Critical, CVSS 10.0GoPublished
openvpn-auth-oauth2 returns FUNC_SUCCESS on client-deny, allowing unauthenticated VPN access
CVE-2026-41070 · GHSA-246w-jgmq-88fg
- Affected
- Go github.com/jkroepke/openvpn-auth-oauth2 >= 1.26.3, < 1.27.3
- Fixed in
- 1.27.3· Vendor fix available
- Issue
- When openvpn-auth-oauth2 is deployed in the experimental plugin mode (shared library loaded by OpenVPN via the plugin directive), clients that do not support WebAuth/SSO (e.g., the openvpn CLI on Linux) are incorrectly admitted to the VPN despite being denied by the authentication logic. The default management-interface mode is not affected because it does not use the OpenVPN plugin return-code mechanism. Impact Authentication bypass — any VPN client that does not advertise WebAuth/SSO support (IVSSO=webauth) is granted full network access without completing OIDC authentication. This affects only deployments running the experimental plugin mode in versions 1.26.3 through 1.27.2. The default and recommended deployment via the management interface is not affected. An unauthenticated attacker can connect to the OpenVPN server using any standard OpenVPN client that does not support webauth (e.g., the Linux openvpn CLI). The plugin correctly issues a client-deny command via the…
Recommended action: Upgrade to 1.27.3 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.