I'm kicking off a series of articles on API Security 🔐 to help us—developers 👨💻👩💻—better understand and implement secure coding in our software design. 🛡️
Here is the seventh one: Server Side Request Forgery
APIs are powerful. But with great power comes great responsibility 🕷️🕸️
One of the most dangerous yet overlooked API vulnerabilities is SSRF (Server Side Request Forgery) – now ranked #7 in the OWASP API Security Top 10 (2023).
So what is SSRF? 🤔
Imagine this:
➡️ An API receives a URL as input and blindly fetches its contents.
➡️ What if that URL points to an internal system like http://localhost:8080/admin?
💥 The API becomes a proxy, letting attackers target internal services not meant to be exposed.
🎯 Common attack scenarios:
🛠️ Scanning internal networks from outside
🗄️ Accessing cloud metadata endpoints (e.g., AWS 169.254.169.254)
🔐 Bypassing firewalls and IP whitelists
🔍 Exfiltrating sensitive data from internal services
🛡️ How to protect your APIs from SSRF:
✅ Validate and sanitize all client-supplied URLs
✅ Avoid using user input directly in network requests
✅ Use allow-lists for safe destinations
✅ Block internal IP ranges (e.g., 127.0.0.1, 169.254.x.x, 10.x.x.x)
✅ Isolate services – follow the principle of least privilege
✅ Monitor and log outbound traffic from your servers
✅ Use SSRF-aware libraries or proxy gateways with built-in protection
🔎 Real-World SSRF Examples:
📦 Capital One breach (2019): SSRF exploited in a WAF led to 100M+ records leaked
☁️ Misconfigured cloud services often become SSRF targets
🧠 Pro tip for developers:
Just because your API doesn’t return data doesn’t mean it’s safe. SSRF can be blind and still deadly.
Let’s build secure-by-design APIs and not leave the door open to internal assets. 🔐
#APIsecurity #OWASP #SSRF #CyberSecurity #DevSecOps #AppSec #OWASPTop10 #SecureCoding #Java #SpringBoot #RESTAPI
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