CVE-2023-40796
📋 TL;DR
This CVE describes a command injection vulnerability in Phicomm K2 routers that allows attackers to execute arbitrary commands via the luci.sys.call function. Attackers can gain unauthorized access and potentially take full control of affected devices. This affects users running vulnerable firmware versions on Phicomm K2 routers.
💻 Affected Systems
- Phicomm K2 router
📦 What is this software?
K2 Firmware by Phicomm
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to install persistent backdoors, intercept network traffic, pivot to internal networks, and use device as part of botnets.
Likely Case
Remote code execution leading to device takeover, credential theft, and network surveillance.
If Mitigated
Limited impact if device is behind firewall with restricted management interface access and proper network segmentation.
🎯 Exploit Status
Exploitation requires authentication to the web interface. Public proof-of-concept code exists in GitHub repositories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch available. Consider upgrading to third-party firmware or replacing device.
🔧 Temporary Workarounds
Restrict Web Interface Access
linuxLimit access to router management interface to trusted IP addresses only
iptables -A INPUT -p tcp --dport 80 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable Web Management Interface
linuxTemporarily disable web interface and use SSH only for management
/etc/init.d/uhttpd stop
/etc/init.d/uhttpd disable
🧯 If You Can't Patch
- Replace affected routers with supported models from different vendors
- Install third-party firmware like OpenWrt or DD-WRT if compatible versions exist
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface at System > Status or via SSH: cat /etc/openwrt_releaseCheck Version:
cat /etc/openwrt_release | grep VERSIONVerify Fix Applied:
Verify firmware version is no longer v22.6.529.216. Check if luci.sys.call function is properly sanitized in updated code.📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in system logs
- Multiple failed login attempts followed by successful login
- Suspicious processes running on router
Network Indicators:
- Unusual outbound connections from router
- DNS queries to suspicious domains
- Unexpected port scans originating from router
SIEM Query:
source="router_logs" AND ("luci.sys.call" OR "command injection" OR "unauthorized access")