OpenVPN 2.1 until v2.4.12 and v2.5.6 may enable authentication bypass in external authentication plug-ins when more than one of them makes use of deferred authentication replies, which allows an external user to be granted access with only partially correct credentials.
The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openvpn | Openvpn | 2.1.0 (including) | 2.4.12 (excluding) |
| Openvpn | Openvpn | 2.5.0 (including) | 2.5.6 (excluding) |
| Openvpn | Ubuntu | bionic | * |
| Openvpn | Ubuntu | devel | * |
| Openvpn | Ubuntu | esm-infra/xenial | * |
| Openvpn | Ubuntu | focal | * |
| Openvpn | Ubuntu | impish | * |
| Openvpn | Ubuntu | jammy | * |
| Openvpn | Ubuntu | kinetic | * |
| Openvpn | Ubuntu | lunar | * |
| Openvpn | Ubuntu | mantic | * |
| Openvpn | Ubuntu | noble | * |
| Openvpn | Ubuntu | trusty | * |
| Openvpn | Ubuntu | trusty/esm | * |
| Openvpn | Ubuntu | upstream | * |
| Openvpn | Ubuntu | xenial | * |