Server -Side Request Forgery (SSRF) is a type of security vulnerability where an attacker exploits an application running on a server to make HTTP or other requests to resources on the internal or external network that should not normally be accessible. Essentially, the attacker convinces the server to make requests to internal IP addresses, such as 127.0.0.1, to cloud metadata services such as AWS (169.254.169.254), to other servers in the same organization, or even to services that are not accessible from the outside environment.
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Such a vulnerability could lead to internal information, internal network reconnaissance, access to sensitive data from cloud services , or even command execution when SSRF is combined with other vulnerabilities. A typical example is when an application allows a user to submit a URL to download an image. If there is no control, the attacker can provide an internal system resource address, such as https://127.0.0.1/admin , and the server will execute the request, revealing information that would otherwise be inaccessible.
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Protecting against SSRF vulnerabilities requires multiple layers of defense. First, all input data related to URLs should be filtered and strictly validated. Ideally, only whitelisted external destinations should be allowed. The server should not be allowed to make external requests unless absolutely necessary. Also, at the network level, it is important to implement firewall restrictions so that the server cannot communicate with internal IP addresses or cloud metadata services.
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At the same time, IAM ( Identity and Access Management ) settings in cloud environments should be limited and allow access to metadata only where necessary. It is also useful to use libraries that do not follow redirects or include built-in protections against SSRF. Finally, it is important to have appropriate logs and monitoring mechanisms to detect suspicious behavior.
