Server-Side Request Forgery (SSRF)

Server-Side Request Forgery (SSRF) occurs when an attacker tricks a vulnerable server into making unauthorized requests to internal or external resources. This can lead to data exfiltration, internal network scanning, cloud metadata exposure, and service exploitation. SSRF is particularly dangerous when applications allow user-controlled URLs or fail to restrict outgoing requests.

Common Vulnerabilities:

• Fetching External URLs Without Proper Validation (e.g., allowing arbitrary URLs in request parameters)
• Accessing Internal Services (e.g., databases, admin panels, cloud metadata APIs)
• SSRF-Based AWS Credentials Theft via the Instance Metadata Service (IMDS)
• Bypassing Network Restrictions to Exploit Internal Systems
• Interacting with Cloud Services (e.g., Kubernetes, Docker APIs) to Gain Unauthorized Access
• Forcing the Application to Perform Malicious Actions on Other Services

To mitigate these risks, applications should validate and restrict user-supplied URLs, enforce allowlists for outgoing requests, block access to internal IP ranges (e.g., 127.0.0.1, 169.254.169.254), and use metadata service version 2 (IMDSv2) in AWS environments. Additionally, logging and monitoring outbound requests can help detect and prevent SSRF exploitation attempts.