CVE-2016-6558
📋 TL;DR
This CVE describes a command injection vulnerability in ASUS RP-AC52 access point firmware that allows remote attackers to execute arbitrary commands with root privileges. The vulnerability exists in the web interface's apply.cgi script where user-controlled input is passed to system() or eval() calls without proper validation. Anyone using affected ASUS RP-AC52 access points with vulnerable firmware versions is at risk.
💻 Affected Systems
- ASUS RP-AC52 access point
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the access point allowing attackers to intercept network traffic, pivot to internal networks, install persistent backdoors, or use the device for botnet activities.
Likely Case
Remote code execution leading to device takeover, network traffic monitoring, and potential lateral movement to connected devices.
If Mitigated
Limited impact if device is behind firewall with restricted web interface access and proper network segmentation.
🎯 Exploit Status
The vulnerability is well-documented with public proof-of-concept code available. Exploitation requires sending a crafted HTTP request to the web interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check ASUS support for latest firmware
Vendor Advisory: https://www.asus.com/support/
Restart Required: Yes
Instructions:
1. Log into ASUS RP-AC52 web interface. 2. Navigate to Administration > Firmware Upgrade. 3. Download latest firmware from ASUS support site. 4. Upload and apply firmware update. 5. Device will reboot automatically.
🔧 Temporary Workarounds
Disable web interface access
linuxBlock external and internal access to the web management interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Network segmentation
allIsolate the access point on separate VLAN with restricted access
🧯 If You Can't Patch
- Immediately isolate the device from critical networks and internet access
- Implement strict firewall rules to only allow necessary management traffic from trusted sources
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under Administration > Firmware Upgrade. If version is 1.0.1.1s or earlier, device is vulnerable.Check Version:
curl -s http://[device-ip]/getcfg.php | grep -i firmwareVerify Fix Applied:
After firmware update, verify version is newer than 1.0.1.1s and test that command injection attempts no longer work.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /apply.cgi
- Commands containing shell metacharacters in HTTP parameters
- Multiple failed login attempts followed by successful command execution
Network Indicators:
- HTTP requests to apply.cgi with action_script parameter containing shell commands
- Unusual outbound connections from the access point
SIEM Query:
source="access-point-logs" AND (uri="/apply.cgi" AND (param="action_script" AND value MATCHES "[;&|`$()]"))