CVE-2023-41350
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to bypass CAPTCHA protection on Chunghwa Telecom NOKIA G-040W-Q routers, enabling automated brute force attacks against authentication systems. Attackers can execute crafted JavaScript to expose CAPTCHA mechanisms, making it easier for bots to compromise router credentials. All users of affected router models with default configurations are vulnerable.
💻 Affected Systems
- Chunghwa Telecom NOKIA G-040W-Q
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise allowing attacker to reconfigure network settings, intercept traffic, deploy malware, or use the router as a pivot point into internal networks.
Likely Case
Unauthorized access to router administration interface leading to network disruption, DNS hijacking, or credential theft from connected devices.
If Mitigated
Limited impact with proper network segmentation, strong authentication policies, and monitoring in place to detect brute force attempts.
🎯 Exploit Status
Exploitation requires JavaScript execution capability but is straightforward once CAPTCHA is bypassed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check with vendor for specific firmware version
Vendor Advisory: https://www.twcert.org.tw/tw/cp-132-7500-0c544-1.html
Restart Required: Yes
Instructions:
1. Contact Chunghwa Telecom or NOKIA for firmware update. 2. Download latest firmware from vendor portal. 3. Access router admin interface. 4. Navigate to firmware update section. 5. Upload and apply new firmware. 6. Reboot router after update completes.
🔧 Temporary Workarounds
Disable Remote Administration
allPrevent external access to router administration interface
Access router admin > Security > Remote Management > Disable
Implement Network Segmentation
allIsolate router management interface to separate VLAN
Configure VLAN for management traffic only
🧯 If You Can't Patch
- Implement rate limiting and account lockout policies for authentication attempts
- Deploy web application firewall (WAF) with CAPTCHA bypass protection rules
🔍 How to Verify
Check if Vulnerable:
Test if CAPTCHA can be bypassed via JavaScript injection on login pageCheck Version:
Login to router admin interface and check firmware version in System StatusVerify Fix Applied:
Verify CAPTCHA protection remains effective after multiple failed login attempts📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts from single IP
- JavaScript errors in web interface logs
- Unusual admin login patterns
Network Indicators:
- HTTP requests attempting to bypass CAPTCHA
- Brute force patterns to router admin interface
SIEM Query:
source="router_logs" AND (event="authentication_failed" count>10 within 5min OR event="javascript_error")