CVE-2025-7531
📋 TL;DR
A critical stack-based buffer overflow vulnerability in Tenda FH1202 routers allows remote attackers to execute arbitrary code by manipulating the 'delno' parameter in the PPTPUserSetting function. This affects Tenda FH1202 routers running firmware version 1.2.0.14(408). Attackers can exploit this without authentication to potentially take full control of affected devices.
💻 Affected Systems
- Tenda FH1202
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, lateral movement into internal networks, persistent backdoor installation, and data exfiltration.
Likely Case
Remote code execution allowing attackers to modify router settings, intercept network traffic, or use the device as a pivot point for further attacks.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering, though internal threats could still exploit the vulnerability.
🎯 Exploit Status
Public exploit details are available on GitHub, making exploitation straightforward for attackers with basic skills.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tenda.com.cn/
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates. 2. If an update is available, download the latest firmware. 3. Log into router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and apply the new firmware. 6. Reboot the router after update completes.
🔧 Temporary Workarounds
Disable PPTP VPN feature
allRemove or disable the PPTP VPN functionality that contains the vulnerable endpoint
Login to router admin interface -> VPN settings -> Disable PPTP VPN
Network segmentation and firewall rules
linuxIsolate affected routers and restrict access to vulnerable endpoints
iptables -A INPUT -p tcp --dport 80 -s trusted_networks -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Immediately isolate affected routers from internet access and place behind firewalls with strict inbound filtering
- Implement network monitoring for exploitation attempts and consider replacing with patched or alternative devices
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via admin interface. If version is exactly 1.2.0.14(408), the device is vulnerable.Check Version:
Login to router web interface at 192.168.0.1 or 192.168.1.1 and check System Status or About pageVerify Fix Applied:
After updating firmware, verify the version has changed from 1.2.0.14(408) to a newer version.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/PPTPUserSetting
- Multiple failed exploitation attempts with malformed delno parameter
- Unexpected router reboots or configuration changes
Network Indicators:
- HTTP POST requests to router IP on port 80/tcp with PPTPUserSetting in URL
- Unusual outbound connections from router to external IPs
SIEM Query:
source="router_logs" AND (url="/goform/PPTPUserSetting" OR "delno=" AND NOT status=200)