🚨 API Security Alert: API7:2023 - Server Side Request Forgery (SSRF) 🚨

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

Additional Resources

• Server Side Request Forgery
• Server-Side Request Forgery Prevention Cheat Sheet
• CWE-918: Server-Side Request Forgery (SSRF)
• URL confusion vulnerabilities in the wild: Exploring parser inconsistencies, Snyk
• Web Security Academy: SSRF