Burp Suite 429 Errors: Troubleshooting

TL;DR

Burp Suite might not show HTTP 429 (Too Many Requests) errors if your browser is caching responses or Burp isn’t intercepting all traffic. This guide helps you fix it by checking browser settings, ensuring Burp intercepts everything, and verifying your Python requests setup.

Troubleshooting Steps

1. Check Browser Cache
   • Browsers often cache responses, including error codes. This means Burp might be seeing a cached ‘good’ response instead of the actual 429.
   • Clear your browser cache and cookies completely for the target domain. The exact steps vary by browser (e.g., Chrome: Settings > Privacy and security > Clear browsing data).
2. Verify Burp Suite Interception
   • Ensure Burp is set to intercept all traffic, at least initially for testing. Go to Proxy > Options > Intercept and make sure ‘Intercept client requests’ and ‘Intercept server responses’ are checked.
   • Confirm the browser proxy settings point to Burp Suite: Typically localhost on port 8080 (or whatever you configured).
   • Check for transparent proxies or other network interference. These can bypass Burp.
3. Burp Suite Scope
   • If you’ve defined a scope in Burp, make sure the target URL is within that scope. Traffic outside the scope might not be fully intercepted or logged.
   • Go to Target > Scope and review your included/excluded URLs.
4. Python Requests Setup
   • Verify your Python code is actually receiving a 429 error: Add explicit error handling.

     import requests
     
     try:
         response = requests.get('your_target_url')
         response.raise_for_status()  # Raise HTTPError for bad responses (4xx or 5xx)
     except requests.exceptions.HTTPError as errh:
         print(f"Http Error: {errh}")
     except requests.exceptions.ConnectionError as errc:
         print(f"Error Connecting: {errc}")
     except Exception as e:
         print(f"Other Error: {e}")
     

   • Check for session persistence issues: If you’re using sessions, ensure they are handled correctly. Incorrectly managed sessions can lead to unexpected 429s.
   • Rate limiting in your code? Double-check that your Python script isn’t intentionally pausing or throttling requests itself.
5. Burp Suite’s Rate Limiter (Advanced)
   • Burp has a built-in rate limiter. It’s unlikely to *hide* 429s, but it’s worth checking if it’s interfering.
   • Go to Project options > Connections > Rate Limiter and review the settings. Reduce or disable limits for testing purposes.
6. Network Configuration
   • Firewalls: Ensure your firewall isn’t blocking traffic between your browser, Burp Suite, and the target server.
   • VPNs/Proxies: If you’re using a VPN or another proxy in addition to Burp, it could be masking the 429 errors. Try disabling them temporarily.