Exploring server-side request forgery

Server-side request forgery (SSRF) is a security vulnerability that’s found within web applications that allows a threat actor to retrieve resources from other systems on the network via the vulnerable web application. For instance, threat actors can gain unauthorized access to resources, perform data exfiltration and remote code execution, and even bypass security controls on a targeted web application. Imagine you’re a threat actor and you’ve discovered a vulnerable web application that allows you to proxy your attacks to other systems on the same network connection, allowing you to perform port scanning and file retrieval.

SSRF is possible when a web application does not validate and sanitize the user-supplied URL during the HTTP request messages. For instance, implementing strict policies for validating all user input against a whitelist of permitted IP addresses or permitted domains. These whitelists can be used to...