WireGuard Easy Cryptographically Weak Token Generation Vulnerability Allowing Information Disclosure

A vulnerability exists in WireGuard Easy versions through 15.3.0, related to the generation of one-time link tokens. The vulnerability allows unauthenticated network attackers to recover WireGuard peer credentials by brute-forcing a limited keyspace of up to 1000 candidate tokens per client ID. The token generation method uses CRC32 over a random value restricted to the range of 0-999, creating a predictable token generation process. Attackers can exploit this vulnerability by enumerating candidate tokens against the unauthenticated '/cnf/:oneTimeLink' route, which lacks rate limiting and does not properly validate token expiration. Successfully exploiting this vulnerability allows attackers to obtain a peer's PrivateKey and PresharedKey, enabling them to impersonate that peer on the VPN network.

Impact

Exploitation of this vulnerability allows for unauthorized recovery of WireGuard peer credentials, specifically the PrivateKey and PresharedKey, which can be used to impersonate a peer on the VPN network.

Reproduction

To reproduce this vulnerability, send requests to the '/cnf/:oneTimeLink' route without authentication. The requests can include candidate tokens generated by applying CRC32 to a random value between 0 and 999. Since the route does not enforce rate limits or check if tokens have expired, it is possible to brute-force the token generation process and retrieve the PrivateKey and PresharedKey of the targeted WireGuard peer.

Remediation

Users can update to WireGuard Easy version 15.3.1 or later, where this vulnerability has been fixed.