CVE-2020-25217
📋 TL;DR
CVE-2020-25217 is a command injection vulnerability in Grandstream GRP261x VoIP phones that allows attackers to execute arbitrary commands as root through the administrative web interface. This affects organizations using these phones with vulnerable firmware, potentially compromising entire phone systems and network segments.
💻 Affected Systems
- Grandstream GRP261x VoIP phones
📦 What is this software?
Grp2612 Firmware by Grandstream
Grp2612p Firmware by Grandstream
Grp2612w Firmware by Grandstream
Grp2613 Firmware by Grandstream
Grp2614 Firmware by Grandstream
Grp2615 Firmware by Grandstream
Grp2616 Firmware by Grandstream
⚠️ Risk & Real-World Impact
Worst Case
Full device compromise leading to lateral movement across the network, data exfiltration, installation of persistent backdoors, and use as pivot points for further attacks.
Likely Case
Unauthorized access to phone configuration, call interception, credential theft, and use in DDoS attacks or cryptocurrency mining.
If Mitigated
Limited to isolated phone compromise if network segmentation and access controls prevent lateral movement.
🎯 Exploit Status
FireEye published detailed technical analysis and proof-of-concept. Exploitation requires network access to administrative interface but no authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware versions after 1.0.3.6
Vendor Advisory: https://www.grandstream.com/support/security-advisories
Restart Required: Yes
Instructions:
1. Download latest firmware from Grandstream support portal. 2. Log into phone web interface. 3. Navigate to Maintenance > Upgrade. 4. Upload firmware file. 5. Reboot phone after upgrade completes.
🔧 Temporary Workarounds
Disable administrative web interface
allDisable the vulnerable web interface if not required for operations
Login to phone web interface > System > Network > Disable HTTP/HTTPS access
Restrict administrative access
linuxLimit access to administrative interface using firewall rules
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
🧯 If You Can't Patch
- Segment VoIP phones on isolated VLAN with strict firewall rules
- Implement network-based intrusion detection to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version in phone web interface: Status > System Status > Firmware VersionCheck Version:
curl -s http://phone-ip/cgi-bin/api-get_system_info | grep firmware_versionVerify Fix Applied:
Verify firmware version is greater than 1.0.3.6 and test administrative interface for command injection📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in system logs
- Multiple failed login attempts to administrative interface
- Unexpected system reboots or configuration changes
Network Indicators:
- HTTP POST requests to /cgi-bin/api-sys_operation with shell metacharacters
- Outbound connections from phones to unusual destinations
- Sudden increase in network traffic from VoIP segment
SIEM Query:
source="voip-phones" AND (url="*cgi-bin/api-sys_operation*" OR cmd="*;*" OR cmd="*|*" OR cmd="*`*")