CVE-2024-37656
📋 TL;DR
An open redirect vulnerability in gnuboard5 v5.5.16 allows attackers to redirect users to malicious websites by exploiting insufficient URL parameter validation in the logout.php file. This affects all websites running the vulnerable version of gnuboard5, potentially enabling phishing attacks and credential theft.
💻 Affected Systems
- gnuboard5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Users are redirected to malicious sites that steal credentials, install malware, or conduct phishing attacks, leading to account compromise and data breaches.
Likely Case
Attackers use the redirect for phishing campaigns, tricking users into entering credentials on fake login pages that resemble legitimate sites.
If Mitigated
With proper input validation and URL filtering, the redirect is blocked or sanitized, preventing successful exploitation.
🎯 Exploit Status
Exploitation requires crafting a malicious URL parameter, which is straightforward due to the lack of validation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check the GitHub issue for updates, as a fix may be in development.
Vendor Advisory: https://github.com/gnuboard/gnuboard5/issues/318
Restart Required: No
Instructions:
1. Monitor the GitHub issue for a patch release. 2. Update gnuboard5 to the patched version once available. 3. Verify the fix by testing the logout.php functionality.
🔧 Temporary Workarounds
Input Validation for URL Parameters
allAdd server-side validation to sanitize or block malicious redirect URLs in the logout.php file.
Edit bbs/logout.php to include URL validation logic, e.g., check if the redirect URL matches allowed domains.
🧯 If You Can't Patch
- Implement a web application firewall (WAF) rule to block open redirect attempts based on URL patterns.
- Monitor and filter outgoing redirects at the network level to detect and block malicious URLs.
🔍 How to Verify
Check if Vulnerable:
Test by accessing logout.php with a crafted redirect parameter (e.g., logout.php?url=http://malicious-site.com) and check if it redirects without validation.Check Version:
Check the gnuboard5 version in the admin panel or configuration files.Verify Fix Applied:
After applying a patch or workaround, retest the same redirect parameter to ensure it is blocked or sanitized.📡 Detection & Monitoring
Log Indicators:
- Unusual redirects in web server logs from logout.php with external URLs.
- Multiple failed redirect attempts or patterns indicating exploitation.
Network Indicators:
- Outbound HTTP requests to suspicious domains triggered by logout.php redirects.
SIEM Query:
Example: source="web_server" AND url="*logout.php*" AND url="*http://*" | stats count by dest_ip