CVE-2021-46378
📋 TL;DR
This vulnerability allows unauthenticated attackers to remotely download configuration files from D-Link DIR850 routers. Attackers can access sensitive router configuration data without credentials. All users of affected DIR850 router versions are impacted.
💻 Affected Systems
- D-Link DIR850
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers obtain router configuration containing credentials, network topology, and security settings, enabling full network compromise and lateral movement.
Likely Case
Attackers steal router configuration to extract Wi-Fi passwords, admin credentials, and network information for unauthorized access.
If Mitigated
With proper network segmentation and firewall rules, impact is limited to the router itself rather than the entire network.
🎯 Exploit Status
Simple HTTP request to vulnerable endpoint; exploit code available in references
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link advisory for latest firmware
Vendor Advisory: https://www.dlink.com/en/security-bulletin/
Restart Required: Yes
Instructions:
1. Visit D-Link support site. 2. Download latest firmware for DIR850. 3. Log into router admin interface. 4. Navigate to firmware update section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Block Configuration Download Endpoint
linuxUse firewall rules to block access to the vulnerable configuration download endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "GET /config.bin" --algo bm -j DROP
Disable Remote Management
allTurn off remote administration in router settings
🧯 If You Can't Patch
- Place router behind firewall with strict inbound rules
- Change all router credentials and Wi-Fi passwords immediately
🔍 How to Verify
Check if Vulnerable:
Attempt to access http://[router-ip]/config.bin without authentication; if configuration file downloads, device is vulnerable.Check Version:
Log into router web interface and check firmware version in System Status or similar sectionVerify Fix Applied:
After patching, attempt same access; should receive authentication prompt or error instead of file download.📡 Detection & Monitoring
Log Indicators:
- HTTP GET requests to /config.bin from external IPs
- Unauthenticated access to configuration endpoints
Network Indicators:
- Unusual downloads of config.bin file
- External IPs accessing router management interface
SIEM Query:
source="router_logs" AND (uri="/config.bin" OR uri="*config*") AND NOT (user="admin" OR auth_success="true")🔗 References
- http://packetstormsecurity.com/files/167042/DLINK-DIR850-Insecure-Direct-Object-Reference.html
- https://drive.google.com/file/d/1S69wOovVa8NRVUXcB0PkVvZHFxREcD4Y/view?usp=sharing
- https://www.dlink.com/en/security-bulletin/
- http://packetstormsecurity.com/files/167042/DLINK-DIR850-Insecure-Direct-Object-Reference.html
- https://drive.google.com/file/d/1S69wOovVa8NRVUXcB0PkVvZHFxREcD4Y/view?usp=sharing
- https://www.dlink.com/en/security-bulletin/
