CVE-2021-35336
📋 TL;DR
CVE-2021-35336 is an authentication bypass vulnerability in Tieline IP Audio Gateway's web administrative interface that allows unauthenticated attackers to access privileged system functions. This affects Tieline IP Audio Gateway versions 2.6.4.8 and earlier. Attackers can gain administrative control without credentials.
💻 Affected Systems
- Tieline IP Audio Gateway
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the audio gateway system, allowing attackers to reconfigure audio routing, intercept communications, disable services, or use the device as a foothold into connected networks.
Likely Case
Unauthorized administrative access leading to service disruption, configuration changes, and potential data interception of audio streams.
If Mitigated
Limited to network reconnaissance if proper network segmentation and access controls prevent exploitation.
🎯 Exploit Status
The Medium article demonstrates exploitation using default credentials or authentication bypass. The vulnerability is simple to exploit with basic web access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 2.6.4.9 or later
Vendor Advisory: https://www.tieline.com/security/
Restart Required: Yes
Instructions:
1. Download latest firmware from Tieline support portal. 2. Backup current configuration. 3. Upload firmware via web interface. 4. Apply update. 5. Reboot device. 6. Restore configuration if needed.
🔧 Temporary Workarounds
Network Isolation
allRestrict access to the web administrative interface using firewall rules or network segmentation.
Disable Web Interface
allIf remote administration is not required, disable the web interface entirely.
🧯 If You Can't Patch
- Implement strict network access controls to limit who can reach the device's management interface
- Monitor for unauthorized access attempts and review authentication logs regularly
🔍 How to Verify
Check if Vulnerable:
Check if web interface allows access to administrative functions without authentication or with default credentials admin/admin.Check Version:
Check version in web interface footer or via SSH: show versionVerify Fix Applied:
Verify firmware version is 2.6.4.9 or later and test that authentication is required for all administrative functions.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated access to admin pages
- Multiple failed login attempts followed by successful admin access
- Configuration changes from unexpected IP addresses
Network Indicators:
- HTTP requests to admin endpoints without authentication headers
- Traffic to device from unexpected sources
SIEM Query:
source="tieline_gateway" AND (url="*/admin*" OR url="*/config*" OR url="*/system*") AND NOT auth_success="true"