Rule Definition
The software does not properly neutralize URLs that are used in an request execution, allowing attackers to access internal services or to launch attacks from your web server.

Remediation
Do not accept URLs from users nor any URLs built with user input. Use authorized sanitization methods.

Violation Code Sample

// JEE
String taintedURL; // value given by an API request
var url = new URL(taintedURL);
HttpURLConnection conn = (HttpURLConnection)url.openConnection(); // Violation

// .NET
String taintedURL; // value given by an API request
var client = new HttpClient();
HttpResponseMessage response = await client.GetAsync(taintedUrl); // Violation

Fixed Code Sample

// JEE
String constURL = "https://www.validUrl.com/";
var url = new URL(constURL);
HttpURLConnection conn = (HttpURLConnection)url.openConnection(); // OK

// .NET
String constURL = "https://www.validUrl.com/";
var client = new HttpClient();
HttpResponseMessage response = await client.GetAsync(constUrl); // OK

https://cwe.mitre.org/data/definitions/918.html https://owasp.org/Top10/A10_2021-Server-Side_Request_Forgery_%28SSRF%29/ https://cheatsheetseries.owasp.org/cheatsheets/Server_Side_Request_Forgery_Prevention_Cheat_Sheet.html