Server-Side Request Forgery (SSRF) in Cloud-Native Microservices
How modern microservices can be coerced into reaching internal APIs, cloud metadata endpoints, and database clusters.
The Anatomy of an SSRF Attack
SSRF occurs when a web application accepts a user-supplied URL (for example, to generate a link preview, export a PDF, or fetch an avatar) and requests that URL directly from the backend server without validation.
Internal Pivot to Cloud Infrastructure
In Kubernetes and cloud environments, backend servers have direct network routing to internal services that are hidden from the public internet—such as internal Redis caches, Consul key-value stores, and cloud metadata services.
Defensive Architecture: Strict URL Parsing & Egress Firewalls
Never rely on blacklist regex filters to block `127.0.0.1` or `localhost`. Implement an egress proxy or network firewall that strictly denies backend server requests to private IP spaces (RFC 1918) and loopback addresses.
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OWASP Top 10: Pragmatic Defensive Countermeasures for Web Engineering Teams
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API Penetration Testing: Identifying BOLA and BFLA Vulnerabilities Before Attackers Do
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