CVE-2021-31659
📋 TL;DR
This CSRF vulnerability in TP-Link managed switches allows attackers to trick administrators into clicking malicious links that can change switch passwords and modify configuration files. It affects TP-Link TL-SG2005, TL-SG2008, and similar models running vulnerable firmware. The vulnerability exists because configuration parameters are passed in URLs without proper anti-CSRF tokens.
💻 Affected Systems
- TP-Link TL-SG2005
- TP-Link TL-SG2008
- TP-Link TL-SG2210
- TP-Link TL-SG2210P
- TP-Link TL-SG2428
- TP-Link TL-SG2428P
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete switch takeover: attacker changes admin password, modifies configuration to redirect traffic, disable security features, or brick the device.
Likely Case
Unauthorized configuration changes leading to network disruption, traffic interception, or denial of service.
If Mitigated
Limited impact if proper network segmentation and admin access controls are in place.
🎯 Exploit Status
Exploitation requires the administrator to be authenticated and click a malicious link. Proof-of-concept code is publicly available on GitHub.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check TP-Link website for latest firmware updates
Vendor Advisory: http://tp-link.com
Restart Required: Yes
Instructions:
1. Log into TP-Link support website. 2. Download latest firmware for your switch model. 3. Access switch web interface. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and apply new firmware. 6. Reboot switch.
🔧 Temporary Workarounds
Restrict Management Access
allLimit switch management interface access to specific trusted IP addresses only.
Configure ACL on upstream firewall/router to restrict access to switch management IP
Use Separate Admin Network
allPlace switch management interfaces on isolated VLAN/network segment.
vlan 99
name MANAGEMENT
interface vlan 99
ip address 10.0.99.1 255.255.255.0
🧯 If You Can't Patch
- Disable web management interface and use CLI/SSH only if supported
- Implement strict browser security policies for admin workstations
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface: System Tools > Firmware Upgrade. If version is 1.0.0 Build 20180529 Rel.40524, device is vulnerable.Check Version:
Show version via CLI or check web interface System Information pageVerify Fix Applied:
After firmware update, verify version has changed from vulnerable version. Test CSRF protection by attempting to modify configuration via crafted URL.📡 Detection & Monitoring
Log Indicators:
- Unexpected configuration changes in switch logs
- Multiple failed login attempts followed by successful password change
- Configuration file modification timestamps
Network Indicators:
- HTTP requests to switch with configuration parameters in URL
- Unusual traffic patterns from switch management interface
SIEM Query:
source="switch_logs" AND (event="password_change" OR event="config_save") AND user="admin"