CVE-2021-27715
📋 TL;DR
This vulnerability allows attackers to bypass authentication on MoFi Network MOFI4500-4GXeLTE-V2 routers and execute arbitrary code via crafted HTTP requests. It affects organizations and individuals using the vulnerable router version, potentially giving attackers full control over the device.
💻 Affected Systems
- MoFi Network MOFI4500-4GXeLTE-V2
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router allowing attackers to intercept all network traffic, install persistent malware, pivot to internal networks, and disable security controls.
Likely Case
Attackers gain administrative access to router, modify network settings, intercept sensitive data, and potentially compromise connected devices.
If Mitigated
Limited impact if device is behind firewall with strict inbound rules and network segmentation prevents lateral movement.
🎯 Exploit Status
Authentication bypass followed by RCE makes exploitation straightforward with publicly available techniques.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor for latest firmware > 3.5.6-xnet-5052
Vendor Advisory: http://mofi.com
Restart Required: Yes
Instructions:
1. Log into router admin interface 2. Navigate to firmware update section 3. Download latest firmware from MoFi website 4. Upload and apply update 5. Reboot router
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router management interface
Access router admin > System > Remote Management > Disable
Restrict management interface access
allLimit management interface to specific IP addresses
Access router admin > Firewall > Add rule to restrict port 80/443 to trusted IPs
🧯 If You Can't Patch
- Place router behind firewall with strict inbound rules blocking all external access to management ports
- Implement network segmentation to isolate router from critical internal systems
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System > FirmwareCheck Version:
Check via web interface or SSH if enabled: cat /etc/versionVerify Fix Applied:
Confirm firmware version is updated beyond 3.5.6-xnet-5052 and test authentication bypass is no longer possible📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts followed by successful admin access
- Unusual HTTP requests to management interface
- Configuration changes from unknown IPs
Network Indicators:
- HTTP requests with crafted authentication bypass payloads
- Unexpected outbound connections from router
- Port scanning from router IP
SIEM Query:
source="router_logs" ("authentication bypass" OR "admin access" from external_ip) OR (http_uri contains "bypass" OR "unauth")