CVE-2020-25506
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on D-Link DNS-320 network storage devices by injecting malicious commands through the system_mgr.cgi component. Attackers can achieve full system compromise without authentication. All users running the affected firmware version are at risk.
💻 Affected Systems
- D-Link DNS-320
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover, data theft, ransomware deployment, and use as pivot point for network attacks.
Likely Case
Remote code execution leading to data exfiltration, malware installation, and device compromise.
If Mitigated
Limited impact if device is isolated behind firewall with no internet exposure.
🎯 Exploit Status
Public exploit code available, trivial to exploit with simple HTTP requests.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to latest firmware from D-Link
Vendor Advisory: https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10183
Restart Required: Yes
Instructions:
1. Download latest firmware from D-Link support site. 2. Login to DNS-320 web interface. 3. Navigate to System > Firmware Update. 4. Upload and apply new firmware. 5. Reboot device.
🔧 Temporary Workarounds
Block web interface access
linuxRestrict access to DNS-320 web management interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable CGI component
linuxRemove or disable vulnerable system_mgr.cgi file
mv /var/www/cgi-bin/system_mgr.cgi /var/www/cgi-bin/system_mgr.cgi.disabled
🧯 If You Can't Patch
- Isolate device on separate VLAN with strict firewall rules
- Disable web management interface and use only local console access
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under System > Firmware Update or via SSH: cat /etc/versionCheck Version:
cat /etc/versionVerify Fix Applied:
Confirm firmware version is updated and test if system_mgr.cgi endpoint responds to command injection attempts📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /cgi-bin/system_mgr.cgi
- Command execution patterns in web logs
- Suspicious shell commands from web process
Network Indicators:
- HTTP requests with shell metacharacters to system_mgr.cgi
- Outbound connections from device to unknown IPs
SIEM Query:
source="web_logs" AND uri="/cgi-bin/system_mgr.cgi" AND (method="POST" OR method="GET") AND (content CONTAINS "|" OR content CONTAINS ";" OR content CONTAINS "`" OR content CONTAINS "$")🔗 References
- https://gist.github.com/WinMin/6f63fd1ae95977e0e2d49bd4b5f00675
- https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10183
- https://www.dlink.com/en/security-bulletin/
- https://gist.github.com/WinMin/6f63fd1ae95977e0e2d49bd4b5f00675
- https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10183
- https://www.dlink.com/en/security-bulletin/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-25506
