Judge0 is an open-source online code execution system. The default configuration of Judge0 leaves the service vulnerable to a sandbox escape via Server Side Request Forgery (SSRF). This allows an attacker with sufficient access to the Judge0 API to obtain unsandboxed code execution as root on the target machine. This vulnerability is fixed in 1.13.1.
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.