CVE-2020-27600
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on D-Link DIR-846 routers via shell metacharacters in Wi-Fi SSID parameters. Attackers can gain full control of affected routers without authentication. All users of vulnerable DIR-846 routers are affected.
💻 Affected Systems
- D-Link DIR-846
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise allowing attackers to intercept all network traffic, install persistent malware, pivot to internal networks, and use the router for botnet activities.
Likely Case
Router takeover leading to DNS hijacking, credential theft from network traffic, and use as a proxy for malicious activities.
If Mitigated
Limited impact if router is behind firewall with restricted WAN access, though still vulnerable to internal attacks.
🎯 Exploit Status
Exploit requires sending a crafted HTTP POST request to the vulnerable endpoint. Public proof-of-concept code is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link security bulletin 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 DIR-846. 3. Log into router admin interface. 4. Navigate to firmware update section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Disable HNAP1 Interface
allDisable the HNAP1 protocol if not required for functionality
Restrict WAN Access
allConfigure firewall to block external access to router admin interface (ports 80/443)
🧯 If You Can't Patch
- Replace router with a different model that receives security updates
- Isolate router in separate VLAN with strict network segmentation
🔍 How to Verify
Check if Vulnerable:
Check if router responds to HNAP1 requests at /HNAP1/control/SetMasterWLanSettings.php endpointCheck Version:
Check router web interface or use nmap script: nmap -sV --script dlink-router-info <router_ip>Verify Fix Applied:
Verify firmware version is newer than A1_100.26 and test exploit no longer works📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /HNAP1/control/SetMasterWLanSettings.php with shell metacharacters in parameters
- Unusual command execution in router logs
Network Indicators:
- Unexpected outbound connections from router
- DNS queries to suspicious domains
- Traffic patterns indicating command-and-control communication
SIEM Query:
source="router_logs" AND uri="/HNAP1/control/SetMasterWLanSettings.php" AND (ssid0="*;*" OR ssid1="*;*")