CVE-2025-41066
📋 TL;DR
Horde Groupware v5.2.22 contains a user enumeration vulnerability that allows unauthenticated attackers to determine valid user accounts by checking responses to specific HTTP requests. This affects all deployments using the vulnerable version, potentially exposing user account information to reconnaissance activities.
💻 Affected Systems
- Horde Groupware
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers build comprehensive user lists for targeted phishing, credential stuffing, or brute force attacks against identified accounts.
Likely Case
Reconnaissance to identify valid users for subsequent attacks, increasing risk of account compromise.
If Mitigated
Limited information disclosure with no direct system compromise if proper authentication and monitoring are in place.
🎯 Exploit Status
Simple HTTP request with specific parameters reveals user existence through response differences.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v5.2.23 or later
Vendor Advisory: https://www.horde.org/apps/groupware
Restart Required: Yes
Instructions:
1. Backup current installation. 2. Download latest version from Horde website. 3. Replace vulnerable files with patched version. 4. Restart web server.
🔧 Temporary Workarounds
Web Application Firewall Rule
allBlock or monitor requests to /imp/attachment.php with id and u parameters
Authentication Requirement
allRequire authentication for /imp/attachment.php endpoint
🧯 If You Can't Patch
- Implement rate limiting on /imp/attachment.php endpoint
- Monitor logs for enumeration attempts and block suspicious IPs
🔍 How to Verify
Check if Vulnerable:
Send HTTP GET request to /imp/attachment.php?id=1&u=testuser and observe if file download occurs for existing vs non-existing usersCheck Version:
Check Horde version in web interface or configuration filesVerify Fix Applied:
After patching, same request should return consistent response regardless of user existence📡 Detection & Monitoring
Log Indicators:
- Multiple requests to /imp/attachment.php with varying u parameter values
- Unusual pattern of file downloads from attachment endpoint
Network Indicators:
- HTTP GET requests to /imp/attachment.php with id and u parameters from single source
SIEM Query:
source="web_logs" AND uri="/imp/attachment.php" AND (parameter="u" OR parameter="id") | stats count by src_ip