CVE-2024-41592
📋 TL;DR
DrayTek Vigor3910 devices have a stack-based buffer overflow vulnerability in the GetCGI function that processes query string parameters. Attackers can exploit this by sending specially crafted HTTP requests with excessive ampersand characters or long key-value pairs, potentially leading to remote code execution. This affects all organizations using vulnerable DrayTek Vigor3910 devices.
💻 Affected Systems
- DrayTek Vigor3910
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with full device compromise, allowing attackers to intercept network traffic, modify configurations, install malware, or pivot to internal networks.
Likely Case
Device crash leading to denial of service, or limited code execution allowing configuration changes and network disruption.
If Mitigated
Denial of service from device crash, requiring physical or console access to restore functionality.
🎯 Exploit Status
Exploitation requires crafting HTTP requests with specific query string patterns. While no public PoC exists, the vulnerability details are sufficiently disclosed for weaponization.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.3.2.7 or later
Vendor Advisory: https://www.draytek.com/support/security-advisory/
Restart Required: Yes
Instructions:
1. Log into Vigor3910 web interface. 2. Navigate to System Maintenance > Firmware Upgrade. 3. Download latest firmware from DrayTek support portal. 4. Upload and apply firmware update. 5. Reboot device after update completes.
🔧 Temporary Workarounds
Disable Web Management Interface
allTemporarily disable the web management interface to prevent exploitation via HTTP requests.
Configure via CLI: system web-management disable
Restrict Management Access
allLimit web management interface access to specific trusted IP addresses only.
Configure via web interface: Management > Access Control > Management from WAN
🧯 If You Can't Patch
- Isolate vulnerable devices in separate network segments with strict firewall rules
- Implement network-based intrusion prevention systems (IPS) to detect and block exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface (System Maintenance > Firmware Information) or CLI (show version). If version is 4.3.2.6 or earlier, device is vulnerable.Check Version:
show versionVerify Fix Applied:
Verify firmware version is 4.3.2.7 or later. Test web interface functionality remains operational after update.📡 Detection & Monitoring
Log Indicators:
- HTTP requests with excessive ampersand characters (&) in query strings
- Device crash/reboot logs
- Unusual configuration changes
Network Indicators:
- HTTP GET/POST requests to device management interface with abnormal query string patterns
- Sudden device unresponsiveness
SIEM Query:
source="vigor3910" AND (http_query CONTAINS "&&&&&&&&" OR http_uri_length > 1000)