CVE-2018-18894
📋 TL;DR
This CVE describes a directory traversal vulnerability in the embedded web server of certain older Lexmark printers. Attackers can exploit this to access files outside the intended directory, potentially exposing sensitive information. Affected devices include specific Lexmark C, M, X, and 6500e series printers manufactured before December 2018.
💻 Affected Systems
- Lexmark C series printers
- Lexmark M series printers
- Lexmark X series printers
- Lexmark 6500e series printers
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attackers to read sensitive configuration files, modify device settings, or potentially execute arbitrary code on the printer.
Likely Case
Unauthorized access to sensitive files containing network credentials, configuration data, or user information stored on the printer.
If Mitigated
Limited impact with proper network segmentation and access controls preventing external access to printer web interfaces.
🎯 Exploit Status
Directory traversal vulnerabilities are well-understood and often exploited using simple HTTP requests with path traversal sequences.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware updates released on or after 2018-12-18
Vendor Advisory: http://support.lexmark.com/index?page=content&id=TE906&locale=EN&userlocale=EN_US
Restart Required: Yes
Instructions:
1. Visit Lexmark support website. 2. Download latest firmware for your specific printer model. 3. Upload firmware via printer web interface or USB. 4. Reboot printer after installation.
🔧 Temporary Workarounds
Disable Embedded Web Server
allTurn off the vulnerable web server component if not required for operations.
Access printer settings via control panel > Network/Ports > Embedded Web Server > Disable
Network Segmentation
allIsolate printers on separate VLAN with restricted access.
🧯 If You Can't Patch
- Implement strict network access controls to limit printer web interface access to authorized IPs only
- Monitor printer network traffic for unusual HTTP requests containing directory traversal patterns
🔍 How to Verify
Check if Vulnerable:
Check printer firmware version via web interface (Settings > Reports > Configuration Report) and compare to patched versions from Lexmark advisory.Check Version:
curl -s http://printer-ip/js/dynamic/printer.config.js | grep 'var firmwareVersion'Verify Fix Applied:
Verify firmware version shows date after 2018-12-18 and attempt directory traversal test requests (e.g., /../../etc/passwd) which should return errors.📡 Detection & Monitoring
Log Indicators:
- HTTP requests containing '../' sequences in URLs
- Access to unusual file paths in web server logs
- Failed authentication attempts to printer admin interface
Network Indicators:
- HTTP requests with path traversal patterns to printer IPs
- Unusual outbound connections from printers
SIEM Query:
source="printer_logs" AND (url="*../*" OR status=403 OR status=404) AND dest_ip="printer_network_range"