ExpressVPN before 12.73.0 on Windows, when split tunneling is used, sends DNS requests according to the Windows configuration (e.g., sends them to DNS servers operated by the user's ISP instead of to the ExpressVPN DNS servers), which may allow remote attackers to obtain sensitive information about websites visited by VPN users.

An integer buffer overflow in the Nginx webserver of ExpressVPN Router version 1 allows remote attackers to obtain sensitive information when the server running as reverse proxy via specially crafted request.

An issue was discovered in ExpressVPN on Windows. The Xvpnd.exe process (which runs as a service with SYSTEM privileges) listens on TCP port 2015, which is used as an RPC interface for communication with the client side of the ExpressVPN application. A JSON-RPC protocol over HTTP is used for communication. The JSON-RPC XVPN.GetPreference and XVPN.SetPreference methods are vulnerable to path traversal, and allow reading and writing files on the file system on behalf of the service.