CVE-2017-7909
📋 TL;DR
This vulnerability allows attackers to bypass authentication on Advantech B+B SmartWorx MESR901 routers by intercepting and modifying web requests. The web interface relies on client-side JavaScript for authentication checks, which can be manipulated. Organizations using these routers with firmware version 1.5.2 or earlier are affected.
💻 Affected Systems
- Advantech B+B SmartWorx MESR901
📦 What is this software?
Mesr901 Firmware by Advantech B\+b Smartworx
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing configuration changes, traffic interception, network pivoting, and potential disruption of industrial control systems.
Likely Case
Unauthorized access to router administration interface leading to configuration changes, network monitoring, and potential credential theft.
If Mitigated
Limited impact if network segmentation prevents external access and proper monitoring detects authentication bypass attempts.
🎯 Exploit Status
Exploitation requires intercepting web traffic but doesn't require special tools beyond basic web proxy.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version after 1.5.2
Vendor Advisory: https://ics-cert.us-cert.gov/advisories/ICSA-17-122-03
Restart Required: Yes
Instructions:
1. Download latest firmware from Advantech support portal. 2. Backup current configuration. 3. Upload new firmware via web interface. 4. Reboot device. 5. Restore configuration if needed.
🔧 Temporary Workarounds
Network Segmentation
allIsolate MESR901 devices from untrusted networks and restrict access to management interface.
Disable Web Interface
allUse alternative management methods (serial console, SSH if available) and disable HTTP/HTTPS management.
🧯 If You Can't Patch
- Implement strict network access controls allowing only trusted IPs to access management interface
- Deploy web application firewall rules to detect and block authentication bypass attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface login page or serial console. If version is 1.5.2 or earlier, device is vulnerable.Check Version:
Check via web interface or serial console using manufacturer-specific commandsVerify Fix Applied:
Verify firmware version is greater than 1.5.2 and test authentication bypass attempts fail.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful access
- Access to admin pages without prior login events
Network Indicators:
- HTTP requests to admin pages without authentication cookies/headers
- Unusual traffic patterns to router management interface
SIEM Query:
source_ip="router_ip" AND (url CONTAINS "/admin/" OR url CONTAINS "/config/") AND NOT (http_cookie CONTAINS "sessionid" OR http_authorization EXISTS)