CVE-2021-31726
📋 TL;DR
CVE-2021-31726 is a remote command injection vulnerability in Akuvox C315 devices that allows attackers to execute arbitrary commands via the cfgd_server service on port 189. This affects Akuvox C315 devices running firmware version 115.116.2613, potentially giving attackers full control over vulnerable devices.
💻 Affected Systems
- Akuvox C315
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, data exfiltration, lateral movement within the network, and use as a botnet node.
Likely Case
Remote code execution allowing attackers to modify device configuration, install malware, or use the device as a pivot point for further attacks.
If Mitigated
Limited impact if devices are behind firewalls with strict network segmentation and access controls.
🎯 Exploit Status
Exploit details are publicly available on Pastebin, showing simple payload injection to port 189.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.akuvox.com/ProductsDisp.aspx?pid=21
Restart Required: No
Instructions:
1. Check Akuvox website for firmware updates
2. Download latest firmware
3. Upload via device web interface
4. Apply update
5. Verify version update
🔧 Temporary Workarounds
Network Access Control
linuxBlock external access to port 189 using firewall rules
iptables -A INPUT -p tcp --dport 189 -j DROP
iptables -A INPUT -p udp --dport 189 -j DROP
Service Binding Restriction
allConfigure cfgd_server to bind to localhost only if possible
🧯 If You Can't Patch
- Segment Akuvox devices on isolated VLAN with strict firewall rules
- Implement network monitoring for unusual traffic to/from port 189
🔍 How to Verify
Check if Vulnerable:
Check if port 189 is listening on all interfaces (0.0.0.0) using netstat or nmap: nmap -p 189 <device_ip>Check Version:
Check device web interface or use SNMP query if enabledVerify Fix Applied:
Verify port 189 is no longer accessible from external networks and device firmware version is updated📡 Detection & Monitoring
Log Indicators:
- Unusual process execution from cfgd_server
- Failed authentication attempts on port 189
- Unexpected configuration changes
Network Indicators:
- Unusual outbound connections from device
- Traffic to port 189 from unexpected sources
- Large data transfers from device
SIEM Query:
source_port:189 OR dest_port:189 AND (protocol:TCP OR protocol:UDP) AND NOT (src_ip:INTERNAL_RANGE AND dest_ip:INTERNAL_RANGE)