CVE-2020-35576
📋 TL;DR
This vulnerability allows authenticated users to execute arbitrary commands as root on TP-Link TL-WR841N V13 (JP) routers via the traceroute feature. Attackers can inject shell metacharacters to gain full system control. Only users with authentication credentials can exploit this vulnerability.
💻 Affected Systems
- TP-Link TL-WR841N V13 (JP)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise allowing attacker to intercept all network traffic, install persistent backdoors, pivot to internal networks, and use router as attack platform.
Likely Case
Local network attacker with router credentials gains root access, modifies router settings, intercepts traffic, and potentially compromises connected devices.
If Mitigated
With proper authentication controls and network segmentation, impact limited to router compromise without lateral movement to other systems.
🎯 Exploit Status
Exploit requires authenticated access. Command injection via traceroute feature is straightforward for attackers with credentials.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version 201216 or later
Vendor Advisory: https://www.tp-link.com/jp/support/download/tl-wr841n/v13/#Firmware
Restart Required: Yes
Instructions:
1. Download latest firmware from TP-Link Japan support site. 2. Log into router web interface. 3. Navigate to System Tools > Firmware Upgrade. 4. Upload firmware file. 5. Wait for upgrade to complete and router to reboot.
🔧 Temporary Workarounds
Disable traceroute feature
allRemove or disable traceroute functionality in router web interface if not needed
Restrict admin access
allLimit router admin interface access to specific IP addresses only
🧯 If You Can't Patch
- Change all router admin passwords to strong, unique credentials
- Isolate router on separate VLAN and restrict access to management interface
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under System Tools > Firmware Upgrade. If version is earlier than 201216, device is vulnerable.Check Version:
Login to router web interface and navigate to System Tools > Firmware Upgrade to view current versionVerify Fix Applied:
After firmware update, verify version shows 201216 or later in System Tools > Firmware Upgrade page.📡 Detection & Monitoring
Log Indicators:
- Unusual traceroute commands in router logs
- Multiple failed login attempts followed by traceroute activity
- Unexpected system command execution
Network Indicators:
- Unusual outbound connections from router
- Traffic redirection or DNS changes
- Router connecting to unexpected external IPs
SIEM Query:
source="router-logs" AND (traceroute OR "system command" OR shell) AND NOT user="legitimate-admin"