Server-Side Request Forgery (SSRF) occurs when an attacker manipulates a web server to make unauthorized internal or external requests, often to access internal resources or exfiltrate data.

A Web Application Firewall (WAF) is the best mitigation because it:

Filters and blocks malicious requests before they reach the server.

Prevents attackers from sending unauthorized requests to internal services.

Can detect and block SSRF patterns in incoming traffic.

Why Not Other Options?

B (CASB) → Used for cloud access control, not effective against SSRF.

C (Forward Proxy) → Helps with outbound traffic control, but SSRF involves incoming requests.

D (MFA) → Helps with authentication but does NOT prevent SSRF attacks.