CVE-2023-25216
📋 TL;DR
CVE-2023-25216 is a critical stack overflow vulnerability in Tenda AC5 routers that allows attackers to cause denial of service or execute arbitrary code by sending a crafted payload to the formSetFirewallCfg function. This affects Tenda AC5 router users running vulnerable firmware versions. Attackers can potentially gain full control of affected devices.
💻 Affected Systems
- Tenda AC5 router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistence installation, network traffic interception, and lateral movement to other devices on the network.
Likely Case
Denial of service causing router crashes and network disruption, potentially followed by malware installation for botnet participation or credential theft.
If Mitigated
Limited to denial of service if exploit attempts are blocked at network perimeter, though internal attacks could still succeed.
🎯 Exploit Status
Public proof-of-concept code exists in GitHub repositories. The vulnerability requires no authentication and has a simple exploitation path.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Tenda website for latest firmware (version after V15.03.06.28)
Vendor Advisory: Not specified in references, check Tenda official website
Restart Required: Yes
Instructions:
1. Log into Tenda router web interface. 2. Navigate to System Tools > Firmware Upgrade. 3. Download latest firmware from Tenda website. 4. Upload and install firmware. 5. Router will reboot automatically.
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router management interface
Log into router > Advanced > System > Remote Management > Disable
Network segmentation
allIsolate router management interface from untrusted networks
Configure firewall rules to block external access to router web interface ports (typically 80/443)
🧯 If You Can't Patch
- Replace affected routers with patched or different vendor models
- Implement strict network access controls to limit who can reach router management interface
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface: System Status > Firmware VersionCheck Version:
curl -s http://router-ip/ | grep -i firmware or check web interfaceVerify Fix Applied:
Verify firmware version is newer than V15.03.06.28 and test that formSetFirewallCfg endpoint handles malformed inputs properly📡 Detection & Monitoring
Log Indicators:
- Multiple failed or malformed requests to /goform/setFirewallCfg endpoint
- Router crash/reboot logs
- Unusual outbound connections from router
Network Indicators:
- Unusual HTTP POST requests to router management interface with large payloads
- Traffic patterns suggesting router compromise
SIEM Query:
source="router_logs" AND (uri="/goform/setFirewallCfg" OR message="firewall config") AND (bytes > 1000 OR status=500)