CVE-2020-29056
📋 TL;DR
This vulnerability allows attackers to escape from a restricted shell and gain root privileges on affected CDATA optical line terminal devices by exploiting the TFTP download configuration feature. It affects multiple CDATA OLT models used in telecommunications networks. Attackers can achieve complete system compromise without authentication.
💻 Affected Systems
- CDATA 72408A
- CDATA 9008A
- CDATA 9016A
- CDATA 92408A
- CDATA 92416A
- CDATA 9288
- CDATA 97016
- CDATA 97024P
- CDATA 97028P
- CDATA 97042P
- CDATA 97084P
- CDATA 97168P
- CDATA FD1002S
- CDATA FD1104
- CDATA FD1104B
- CDATA FD1104S
- CDATA FD1104SN
- CDATA FD1108S
- CDATA FD1204S-R2
- CDATA FD1204SN
- CDATA FD1204SN-R2
- CDATA FD1208S-R2
- CDATA FD1216S-R1
- CDATA FD1608GS
- CDATA FD1608SN
- CDATA FD1616GS
- CDATA FD1616SN
- CDATA FD8000
📦 What is this software?
9288 Firmware by Cdatatec
9288 Firmware by Cdatatec
9288 Firmware by Cdatatec
9288 Firmware by Cdatatec
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover with root access, allowing attackers to modify configurations, intercept network traffic, install persistent backdoors, or disable the device entirely.
Likely Case
Unauthorized root access leading to network disruption, data interception, or device reconfiguration for malicious purposes.
If Mitigated
Limited impact if devices are isolated from untrusted networks and TFTP services are disabled or restricted.
🎯 Exploit Status
Exploitation details are publicly documented in the referenced blog posts, showing how to escape restricted shell via TFTP configuration download.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
Contact CDATA vendor for firmware updates. No official patch information is publicly available at this time.
🔧 Temporary Workarounds
Disable TFTP Configuration Downloads
allDisable TFTP service for configuration downloads on affected devices
Access device CLI and disable TFTP configuration download feature
Network Segmentation
allIsolate affected devices from untrusted networks and restrict TFTP access
Configure firewall rules to block TFTP (port 69) from untrusted sources
🧯 If You Can't Patch
- Segment affected devices in isolated network zones with strict access controls
- Implement network monitoring for TFTP traffic and shell escape attempts
🔍 How to Verify
Check if Vulnerable:
Check if device model is in affected list and TFTP configuration download is enabledCheck Version:
show version (device-specific command)Verify Fix Applied:
Verify TFTP service is disabled or restricted, and test shell escape attempts fail📡 Detection & Monitoring
Log Indicators:
- TFTP configuration download attempts
- Shell escape sequences in logs
- Unauthorized root access events
Network Indicators:
- TFTP traffic to affected devices
- Unexpected shell commands over network
SIEM Query:
source_port:69 AND dest_ip:[affected_device_ips] OR event_type:"shell_escape"