CVE-2023-36355
📋 TL;DR
This vulnerability in TP-Link TL-WR940N V4 routers allows attackers to trigger a buffer overflow via the ipStart parameter in the web interface. Attackers can cause Denial of Service (DoS) through crafted GET requests, potentially disrupting network connectivity. Only users of TP-Link TL-WR940N V4 routers are affected.
💻 Affected Systems
- TP-Link TL-WR940N
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router crash requiring physical reboot, potential remote code execution if buffer overflow can be controlled to execute arbitrary code
Likely Case
Router becomes unresponsive, requiring reboot to restore functionality, disrupting all network services
If Mitigated
Limited impact if router is behind firewall with restricted web interface access
🎯 Exploit Status
Exploit requires authentication to web interface, but many users keep default credentials
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not provided in CVE references
Restart Required: Yes
Instructions:
1. Check TP-Link support site for firmware updates
2. Download latest firmware for TL-WR940N V4
3. Access router web interface
4. Navigate to System Tools > Firmware Upgrade
5. Upload and apply new firmware
6. Router will reboot automatically
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to web interface
Access router web interface > Security > Remote Management > Disable
Change default credentials
allPrevent unauthorized access to web interface
Access router web interface > System Tools > Password > Set strong password
🧯 If You Can't Patch
- Place router behind firewall with strict inbound rules blocking web interface ports (typically 80/443)
- Implement network segmentation to isolate router from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Check router model and version in web interface (Status > Router Information), confirm TL-WR940N V4Check Version:
Access router web interface and navigate to Status > Router InformationVerify Fix Applied:
Verify firmware version is updated to latest available from TP-Link📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by GET requests to /userRpm/WanDynamicIpV6CfgRpm with long ipStart parameters
- Router reboot events without user action
Network Indicators:
- Unusual HTTP traffic to router web interface on port 80/443 with crafted GET parameters
- Sudden loss of router responsiveness
SIEM Query:
source="router.log" AND (uri="/userRpm/WanDynamicIpV6CfgRpm" AND param="ipStart" AND length(param_value)>100)🔗 References
- http://packetstormsecurity.com/files/173294/TP-Link-TL-WR940N-4-Buffer-Overflow.html
- https://github.com/a101e-IoTvul/iotvul/blob/main/tp-link/9/TP-Link%20TL-WR940N%20wireless%20router%20userRpmWanDynamicIpV6CfgRpm%20buffer%20write%20out-of-bounds%20vulnerability.md
- http://packetstormsecurity.com/files/173294/TP-Link-TL-WR940N-4-Buffer-Overflow.html
- https://github.com/a101e-IoTvul/iotvul/blob/main/tp-link/9/TP-Link%20TL-WR940N%20wireless%20router%20userRpmWanDynamicIpV6CfgRpm%20buffer%20write%20out-of-bounds%20vulnerability.md
