CVE-2016-4503
📋 TL;DR
This vulnerability allows remote attackers to bypass authentication in Moxa Device Server Web Console 5232-N by manipulating cookie parameters containing UserId values. Attackers can modify device settings and data without valid credentials. This affects all deployments of the vulnerable Moxa device server software.
💻 Affected Systems
- Moxa Device Server Web Console 5232-N
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of industrial control systems, unauthorized configuration changes leading to operational disruption, data manipulation or destruction, and potential physical safety risks in industrial environments.
Likely Case
Unauthorized access to device management interface, modification of network settings, disruption of industrial communications, and potential lateral movement within industrial networks.
If Mitigated
Limited impact with proper network segmentation, authentication controls, and monitoring in place, potentially only affecting isolated systems.
🎯 Exploit Status
Simple cookie manipulation attack requiring only web access to the management interface. Public advisories and exploit details are available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Moxa security advisory for specific patched version
Vendor Advisory: https://www.moxa.com/en/support/product-support/security-advisory/moxa-device-server-web-console-5232-n-authentication-bypass-vulnerability
Restart Required: Yes
Instructions:
1. Check current firmware version. 2. Download patched firmware from Moxa support portal. 3. Backup current configuration. 4. Upload and install new firmware via web interface. 5. Verify installation and restore configuration if needed.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Moxa devices in separate VLANs with strict firewall rules limiting access to management interfaces.
Access Control Lists
linuxImplement IP-based access restrictions to only allow trusted management stations to connect to the web interface.
iptables -A INPUT -p tcp --dport 80 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected devices from untrusted networks
- Deploy web application firewall (WAF) rules to detect and block cookie manipulation attempts
🔍 How to Verify
Check if Vulnerable:
Attempt to access management interface with manipulated UserId cookie parameter and check if authentication is bypassed.Check Version:
Check firmware version via web interface or SSH: show versionVerify Fix Applied:
After patching, verify that cookie manipulation no longer bypasses authentication and proper login is required.📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts followed by successful access without valid credentials
- Access to administrative pages from unauthorized IP addresses
- Cookie manipulation attempts in web server logs
Network Indicators:
- HTTP requests with manipulated cookie parameters to management interface
- Unauthorized configuration changes via web interface
SIEM Query:
source="web_logs" AND (url="*/admin*" OR url="*/config*") AND NOT (user="admin" OR auth_success="true")