CVE-2023-43959
📋 TL;DR
This vulnerability allows remote attackers with administrative access to execute arbitrary code on Yealink SIP-T19P E2 phones via a crafted request to the diagnostic ping function. Attackers can gain full control of affected devices, potentially compromising voice communications and network security. Organizations using these phones with vulnerable firmware are affected.
💻 Affected Systems
- Yealink SIP-T19P E2
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover leading to eavesdropping on calls, credential theft, lateral movement to internal networks, and persistent backdoor installation.
Likely Case
Remote code execution allowing attackers to disrupt phone services, intercept communications, and use devices as footholds for further attacks.
If Mitigated
Limited impact if devices are isolated in separate VLANs with strict network segmentation and administrative access controls.
🎯 Exploit Status
Exploit requires admin credentials but is straightforward to execute once credentials are obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not publicly available
Restart Required: Yes
Instructions:
1. Check Yealink support portal for firmware updates
2. Download latest firmware if available
3. Upload firmware to phone via web interface
4. Reboot phone after update
5. Verify firmware version is updated
🔧 Temporary Workarounds
Disable Diagnostic Ping Function
allRemove or restrict access to the diagnostic ping functionality in web interface
Network Segmentation
allIsolate VoIP phones in separate VLAN with strict firewall rules
🧯 If You Can't Patch
- Change all administrative passwords to strong, unique credentials
- Implement network access control to restrict phone management interfaces to authorized IPs only
🔍 How to Verify
Check if Vulnerable:
Check firmware version via phone web interface: System Status > Version InformationCheck Version:
Not applicable - check via web interface or phone displayVerify Fix Applied:
Verify firmware version is no longer v.53.84.0.15 and test diagnostic ping function is restricted📡 Detection & Monitoring
Log Indicators:
- Unusual diagnostic ping requests
- Multiple failed login attempts to admin interface
- Unexpected system command execution
Network Indicators:
- Unusual traffic from phone to external IPs
- HTTP POST requests to diagnostic endpoints
- Abnormal port scanning from phone
SIEM Query:
source="voip-phone" AND (event="diagnostic_ping" OR event="command_execution")