Definition
Server-side request forgery, or SSRF, is a web security vulnerability that allows an attacker to trick a server into making unintended requests to internal or external resources on the attacker's behalf. This occurs when an application fetches a remote resource without properly validating the user-supplied URL, enabling the attacker to manipulate the server's network access. Understanding SSRF is crucial for developers and security professionals to prevent unauthorized data access or system compromise. For instance, an attacker might exploit an SSRF vulnerability to scan internal network ports or access cloud metadata services. Unlike cross-site scripting (XSS) which targets the user's browser, SSRF targets the server itself. This vulnerability is a key topic covered in certifications like CompTIA Security+ and CySA+, as well as the CISSP exam.