CVE-2023-24333
📋 TL;DR
A stack overflow vulnerability in Tenda AC21 routers allows attackers to execute arbitrary commands via crafted POST requests to the /goform/openSchedWifi endpoint. This affects Tenda AC21 devices with specific firmware versions, potentially enabling remote code execution on vulnerable routers.
💻 Affected Systems
- Tenda AC21
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept traffic, modify DNS settings, install persistent malware, and pivot to internal networks.
Likely Case
Router takeover leading to network disruption, credential theft from connected devices, and potential lateral movement within the network.
If Mitigated
Limited impact if router is behind firewall with restricted WAN access and proper network segmentation.
🎯 Exploit Status
Public proof-of-concept code exists in GitHub repositories. Exploitation requires sending a crafted HTTP POST request to the vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not publicly available
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates. 2. Download latest firmware for AC21 model. 3. Access router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and install new firmware. 6. Reboot router after installation.
🔧 Temporary Workarounds
Block External Access to Router Admin
allConfigure firewall to block WAN access to router administration interface (typically port 80/443).
Disable Remote Management
allTurn off remote management feature in router settings to prevent external access to admin interface.
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict firewall rules limiting traffic to/from the device.
- Implement network monitoring for suspicious POST requests to /goform/openSchedWifi endpoint.
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version matches US_AC21V1.0re_V16.03.08.15_cn_TDC01, device is vulnerable.Check Version:
Login to router admin interface and check System Status or Firmware Update section for version information.Verify Fix Applied:
After firmware update, verify version no longer matches vulnerable version and test that POST requests to /goform/openSchedWifi no longer cause issues.📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /goform/openSchedWifi with unusual payloads
- Router reboot events following POST requests
- Unusual command execution in router logs
Network Indicators:
- HTTP traffic to router IP on port 80/443 with POST to /goform/openSchedWifi
- Unusual outbound connections from router
SIEM Query:
source="router_logs" AND (uri="/goform/openSchedWifi" OR method="POST") AND (payload_size>1000 OR contains(payload,"cmd") OR contains(payload,"exec"))