CVE-2020-28929
📋 TL;DR
CVE-2020-28929 allows unauthenticated attackers to remotely download server logs containing administrative hashed credentials via a specific URI in EPSON EPS TSE Server 8. This affects organizations using EPSON TSE Server 8 version 21.0.11 for tax compliance in point-of-sale systems.
💻 Affected Systems
- EPSON EPS TSE Server 8
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers obtain administrative credentials, gain full control of the TSE server, manipulate transaction logs, compromise tax compliance, and potentially pivot to other systems.
Likely Case
Attackers retrieve hashed admin credentials, crack them offline, gain administrative access to the TSE server, and potentially alter or delete transaction logs.
If Mitigated
With proper network segmentation and access controls, attackers cannot reach the vulnerable endpoint, limiting impact to isolated systems.
🎯 Exploit Status
Exploitation requires only a single HTTP GET request to the vulnerable endpoint. The vulnerability details and proof-of-concept are publicly documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 21.0.12 or later
Vendor Advisory: https://www.epson.de/support/s?language=de_DE&query=TSE+Server+8+Security+Update
Restart Required: Yes
Instructions:
1. Download the latest EPSON TSE Server 8 update from the official EPSON website. 2. Backup current configuration and data. 3. Run the installer with administrative privileges. 4. Restart the TSE Server service. 5. Verify the update by checking the version number.
🔧 Temporary Workarounds
Network Access Control
windowsRestrict access to the TSE Server web interface to trusted IP addresses only.
Use Windows Firewall: New-InboundFirewallRule -DisplayName "Block TSE Web Interface" -Direction Inbound -Protocol TCP -LocalPort 80,443 -Action Block -RemoteAddress Any
Then create allow rules for specific IPs: New-InboundFirewallRule -DisplayName "Allow TSE Admin" -Direction Inbound -Protocol TCP -LocalPort 80,443 -Action Allow -RemoteAddress 192.168.1.0/24
Web Server Configuration
allAdd authentication requirements to the maintenance/troubleshoot.php endpoint.
For Apache: Add to .htaccess: AuthType Basic\nAuthName "Restricted Access"\nAuthUserFile /path/to/.htpasswd\nRequire valid-user
For IIS: Enable Windows Authentication and disable Anonymous Authentication for the specific directory
🧯 If You Can't Patch
- Isolate the TSE Server on a dedicated network segment with strict firewall rules allowing only necessary traffic from authorized systems.
- Implement network monitoring and intrusion detection to alert on access attempts to the vulnerable endpoint.
🔍 How to Verify
Check if Vulnerable:
Attempt to access http://[TSE_SERVER_IP]/maintenance/troubleshoot.php?download=1 from an unauthenticated session. If it returns log files containing credential hashes, the system is vulnerable.Check Version:
Check the version in the TSE Server administration interface or look for version files in the installation directory.Verify Fix Applied:
After patching, attempt the same access. It should return an error or require authentication. Check the server version is 21.0.12 or higher.📡 Detection & Monitoring
Log Indicators:
- HTTP GET requests to /maintenance/troubleshoot.php?download=1 from unauthenticated sources
- Unusual access patterns to the TSE Server web interface
Network Indicators:
- HTTP traffic to port 80/443 containing the string "troubleshoot.php?download=1"
- Outbound connections from the TSE server to unknown IPs after compromise
SIEM Query:
source="TSE_Server_Logs" AND uri="/maintenance/troubleshoot.php" AND args="download=1" AND user="-"