CVE-2021-25328
📋 TL;DR
This vulnerability allows an authenticated attacker to exploit a buffer overflow in the Skyworth RN510 router's web interface. By sending a specially crafted request to the /cgi-bin/app-staticIP.asp endpoint, attackers can cause denial of service or potentially execute arbitrary code on the device. This affects users of Skyworth RN510 routers running vulnerable firmware versions.
💻 Affected Systems
- Skyworth Digital Technology RN510
📦 What is this software?
Rn510 Firmware by Skyworthdigital
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistent backdoor installation, and lateral movement to connected networks.
Likely Case
Denial of service causing router instability or crashes, disrupting network connectivity for all users.
If Mitigated
Limited impact if proper network segmentation and access controls prevent unauthorized access to the management interface.
🎯 Exploit Status
Exploit code is publicly available, making this easily weaponizable by attackers with basic skills.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check vendor website for firmware updates
2. If update available, download and verify checksum
3. Access router admin interface
4. Navigate to firmware update section
5. Upload new firmware file
6. Wait for update to complete
7. Reboot router
🔧 Temporary Workarounds
Disable web management interface
allPrevent access to the vulnerable endpoint by disabling the web management interface if not needed.
Router-specific - check admin interface for web management toggle
Restrict management access
allLimit access to the router's management interface to trusted IP addresses only.
Router-specific - configure firewall rules to restrict access to management ports
🧯 If You Can't Patch
- Isolate vulnerable routers in separate network segments with strict firewall rules
- Change default credentials and implement strong authentication mechanisms
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via admin interface or by accessing http://router-ip/status.aspCheck Version:
curl -s http://router-ip/status.asp | grep -i versionVerify Fix Applied:
Verify firmware version has been updated to a version later than V.3.1.0.4📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by POST requests to /cgi-bin/app-staticIP.asp
- Unusual large payloads sent to the static IP configuration endpoint
Network Indicators:
- Unusual traffic patterns to router management interface from unauthorized sources
- POST requests with abnormally long parameters to the vulnerable endpoint
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/app-staticIP.asp" AND (bytes_out>10000 OR status=500))🔗 References
- http://packetstormsecurity.com/files/162450/Shenzhen-Skyworth-RN510-Buffer-Overflow.html
- http://seclists.org/fulldisclosure/2021/May/5
- https://s3curityb3ast.github.io/KSA-Dev-011.md
- http://packetstormsecurity.com/files/162450/Shenzhen-Skyworth-RN510-Buffer-Overflow.html
- http://seclists.org/fulldisclosure/2021/May/5
- https://s3curityb3ast.github.io/KSA-Dev-011.md
