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Introduction
Blind Server-Side Request Forgery (SSRF) is a critical vulnerability that allows attackers to force a server to make unintended requests. Detecting it can be challenging, but Burp Suite offers powerful techniques to uncover these hidden flaws. This guide walks you through a proven method using Burp Suite Intruder and Collaborator to identify Blind SSRF efficiently.
Learning Objectives
- Learn how to use Burp Suite Intruder for header bruteforcing.
- Understand how Burp Collaborator helps detect out-of-band vulnerabilities.
- Master the Taborator extension for monitoring Blind SSRF hits.
- Setting Up Burp Suite Intruder for Header Bruteforcing
Command/Tool Used:
GET /api/v1/user HTTP/1.1 Host: target.com X-Forwarded-For: §collaborator-url§
Step-by-Step Guide:
- Intercept a Request – Capture a target request in Burp Proxy.
- Send to Intruder – Right-click the request and select “Send to Intruder.”
- Configure Payload Positions – Use Pitchfork mode and mark headers like
X-Forwarded-For,X-Real-IP, etc. - Insert Collaborator URL – Replace the payload position with a Burp Collaborator URL.
2. Leveraging Burp Collaborator for Blind SSRF Detection
Command/Tool Used:
User-Agent: Mozilla/5.0 (Burp Collaborator Test)
Step-by-Step Guide:
- Generate a Collaborator Payload – Go to Burp → Collaborator → Copy to clipboard.
- Inject Payload into Headers – Insert the URL into headers like:
X-Forwarded-Host: abc123.collaborator.com
- Monitor for Interactions – Check the Collaborator tab for DNS/HTTP hits indicating SSRF.
3. Using Taborator Extension for Real-Time Monitoring
Tool Used:
Step-by-Step Guide:
- Install Taborator – Load the extension via Burp’s Extender → Add → Select JAR file.
- Automate Monitoring – Taborator auto-logs Collaborator interactions, reducing manual checks.
- Filter False Positives – Use regex to filter noise and focus on valid SSRF hits.
4. Advanced Payload Techniques for Blind SSRF
Command/Tool Used:
POST /admin HTTP/1.1 Host: target.com X-Custom-IP: 127.0.0.1
Step-by-Step Guide:
- Use Numerical Payloads – Test internal IP ranges (
192.168.§1-255§.1). - Enumerate Cloud Metadata Endpoints – Target AWS/GCP metadata services:
GET http://169.254.169.254/latest/meta-data/
- Check for Open Redirects – Some SSRF chains with redirects (e.g.,
?url=//attacker.com).
5. Automating SSRF Detection with Python
Code Snippet:
import requests
headers = {
"X-Forwarded-For": "http://burpcollaborator.net",
}
response = requests.get("https://target.com/api/data", headers=headers)
print("Check Collaborator for hits!")
Step-by-Step Guide:
- Script Automation – Run multiple header injections programmatically.
- Integrate with Burp API – Use `burp-rest-api` for automated scans.
- Log Analysis – Parse Collaborator logs for successful exploitations.
What Undercode Say:
- Key Takeaway 1: Blind SSRF is often missed in manual testing; automation (Burp + Collaborator) is key.
- Key Takeaway 2: Internal service exposure via SSRF can lead to cloud credential theft or ransomware attacks.
Analysis:
Blind SSRF remains a high-risk vulnerability due to its potential to bypass firewalls and access internal systems. With cloud adoption rising, attackers increasingly exploit SSRF to steal IAM roles or pivot into private networks. Proactive testing using Burp Suite’s advanced tooling is essential for modern AppSec teams.
Prediction:
As APIs and microservices grow, SSRF attacks will evolve into cloud-focused exploits (e.g., AWS SSM, GCP Workload Identity). Future defenses will require stricter egress controls and runtime request validation. Organizations must prioritize SSRF testing in CI/CD pipelines to prevent data breaches.
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IT/Security Reporter URL:
Reported By: Deepak Saini – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
