CVE-2024-39097
📋 TL;DR
This CVE describes an Open Redirect vulnerability in Gnuboard v6.0.4 and earlier versions. Attackers can manipulate the 'url' parameter in the login path to redirect users to malicious websites after authentication. All users running vulnerable Gnuboard installations are affected.
💻 Affected Systems
- Gnuboard
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could redirect authenticated users to phishing sites that steal credentials or deliver malware, potentially leading to account compromise or system infection.
Likely Case
Attackers use the redirect for phishing campaigns, tricking users into visiting malicious sites that may steal session cookies or credentials.
If Mitigated
With proper input validation and URL whitelisting, the impact is limited to failed redirect attempts with no security compromise.
🎯 Exploit Status
The vulnerability requires no authentication and exploitation is straightforward via URL parameter manipulation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit eb52096f8328a891879066400f4599d1153d8bf2
Vendor Advisory: https://github.com/gnuboard/g6/issues/557
Restart Required: No
Instructions:
1. Update to the latest Gnuboard version. 2. Apply the patch from commit eb52096f8328a891879066400f4599d1153d8bf2. 3. Verify the 'url' parameter validation is properly implemented.
🔧 Temporary Workarounds
Input Validation Filter
allAdd server-side validation to only allow relative URLs or whitelisted domains in the 'url' parameter.
Modify login.php to validate the 'url' parameter before processing
WAF Rule
allImplement a web application firewall rule to block redirects to external domains from the login endpoint.
Add WAF rule: Block requests to /login with 'url' parameter containing 'http://' or 'https://' to external domains
🧯 If You Can't Patch
- Implement strict Content Security Policy (CSP) headers to restrict redirect destinations
- Monitor and block suspicious redirect patterns in web server logs
🔍 How to Verify
Check if Vulnerable:
Test by accessing the login page with a malicious 'url' parameter (e.g., /login?url=http://evil.com) and check if redirect occurs.Check Version:
Check Gnuboard version in admin panel or via file version metadataVerify Fix Applied:
After patching, test the same malicious URL parameter and verify it's blocked or sanitized.📡 Detection & Monitoring
Log Indicators:
- Unusual redirect patterns in access logs
- Multiple failed login attempts with external URLs in parameters
Network Indicators:
- HTTP 302 redirects to external domains from login endpoints
- Suspicious referrer headers
SIEM Query:
source="web_logs" AND uri_path="/login" AND query_string="*url=*" AND status=302