CVE-2020-12774
📋 TL;DR
This vulnerability in D-Link DSL-7740C routers allows authenticated LAN users to execute arbitrary commands through improper input validation. Attackers with LAN access can gain elevated privileges and potentially take full control of the device. Only users of this specific router model are affected.
💻 Affected Systems
- D-Link DSL-7740C
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, modify DNS settings, install persistent backdoors, and pivot to other devices on the network.
Likely Case
Local attacker gains administrative access to the router, enabling network reconnaissance, traffic monitoring, and potential credential theft from connected devices.
If Mitigated
With proper network segmentation and access controls, impact limited to isolated network segment with no critical assets.
🎯 Exploit Status
Exploit requires LAN access and valid credentials; trivial to execute once authenticated
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link support for latest firmware
Vendor Advisory: https://support.dlink.com/
Restart Required: Yes
Instructions:
1. Log into router admin interface 2. Navigate to firmware update section 3. Download latest firmware from D-Link support site 4. Upload and apply firmware update 5. Reboot router
🔧 Temporary Workarounds
Restrict LAN Access
allImplement network segmentation to limit which devices can access router management interface
Change Default Credentials
allUse strong, unique admin credentials to reduce attack surface
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict access controls
- Disable remote management and limit admin access to specific trusted IP addresses
🔍 How to Verify
Check if Vulnerable:
Check firmware version against D-Link security advisory; test with authenticated command injection attemptsCheck Version:
Log into router web interface and check System Status or About pageVerify Fix Applied:
Verify firmware version is updated and test command injection attempts fail📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in router logs
- Multiple failed login attempts followed by successful login
Network Indicators:
- Unexpected outbound connections from router
- DNS changes not initiated by administrator
SIEM Query:
source="router" AND (command="*sh*" OR command="*cat*" OR command="*wget*")