CVE-2022-30040
📋 TL;DR
CVE-2022-30040 is a buffer overflow vulnerability in Tenda AX1803 routers that allows attackers to cause denial of service by sending specially crafted HTTP requests to the SetSysTimeCfg endpoint. Attackers can exploit this remotely without authentication by manipulating the ntpserve parameter. This affects all users running vulnerable firmware versions of the Tenda AX1803 router.
💻 Affected Systems
- Tenda AX1803
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router crash and persistent denial of service requiring physical reset, potentially allowing for remote code execution if the overflow can be controlled precisely.
Likely Case
Router becomes unresponsive or reboots, causing temporary network disruption for all connected devices.
If Mitigated
No impact if the vulnerable endpoint is blocked or the router is not internet-facing.
🎯 Exploit Status
Multiple public proof-of-concept scripts exist demonstrating the denial of service attack. The exploit requires sending a simple HTTP POST request with a long ntpserve parameter.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates. 2. If available, download the latest firmware. 3. Access router admin panel. 4. Navigate to firmware upgrade section. 5. Upload and apply the new firmware. 6. Wait for router to reboot.
🔧 Temporary Workarounds
Block Web Interface from WAN
allDisable remote management/administration to prevent external exploitation
Access router admin panel -> System -> Remote Management -> Disable
Firewall Rule to Block SetSysTimeCfg Endpoint
linuxBlock access to the vulnerable endpoint using firewall rules
iptables -A INPUT -p tcp --dport 80 -m string --string "goform/SetSysTimeCfg" --algo bm -j DROP
🧯 If You Can't Patch
- Replace the vulnerable router with a different model or brand
- Place router behind an additional firewall that blocks all HTTP traffic to the router's IP
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin panel under System Status. If version is v1.0.0.1_2890 or earlier, likely vulnerable.Check Version:
curl -s http://router-ip/login/Auth | grep version or check admin panelVerify Fix Applied:
After firmware update, verify version has changed from v1.0.0.1_2890. Test by attempting to access http://[router-ip]/goform/SetSysTimeCfg - should not cause crash.📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/SetSysTimeCfg
- Router crash/reboot logs
- Unusually long ntpserve parameter values in HTTP logs
Network Indicators:
- HTTP POST requests to router IP on port 80 with path containing SetSysTimeCfg
- Sudden loss of connectivity to router
SIEM Query:
source="router_logs" AND (url="/goform/SetSysTimeCfg" OR message="crash" OR message="reboot")