CVE-2025-25632: Tenda AC15 Firmware RCE Vulnerability

CVE-2025-25632 Overview

CVE-2025-25632 is a critical command injection vulnerability affecting Tenda AC15 wireless routers running firmware version 15.03.05.19. The vulnerability exists in the handler function located at /goform/telnet, which fails to properly sanitize user-supplied input before passing it to system command execution functions. This allows remote unauthenticated attackers to execute arbitrary commands on the affected device with root privileges.

Critical Impact

Remote attackers can achieve complete device compromise through unauthenticated command injection, potentially leading to network infrastructure takeover, lateral movement, and persistent backdoor installation.

Affected Products

• Tenda AC15 Firmware version 15.03.05.19
• Tenda AC15 Hardware devices running vulnerable firmware

Discovery Timeline

• 2025-03-05 - CVE-2025-25632 published to NVD
• 2025-04-09 - Last updated in NVD database

Technical Details for CVE-2025-25632

Vulnerability Analysis

This command injection vulnerability (CWE-77) resides in the web management interface of Tenda AC15 routers. The /goform/telnet endpoint contains a handler function that processes user input without adequate sanitization. When malicious input containing shell metacharacters is submitted to this endpoint, the embedded commands are executed directly on the underlying Linux operating system with root privileges.

The attack requires no authentication, making it particularly dangerous for devices exposed to the internet or accessible from untrusted network segments. Successful exploitation grants attackers full control over the router, enabling them to intercept network traffic, modify DNS settings, pivot to internal network resources, or enroll the device into a botnet.

Root Cause

The root cause is improper input validation in the telnet handler function. User-controlled parameters are concatenated directly into system command strings without proper sanitization or escaping of shell metacharacters such as semicolons (;), pipes (|), backticks (`), and command substitution syntax ($()). This allows attackers to break out of the intended command context and inject arbitrary commands.

Attack Vector

The vulnerability is exploitable over the network without authentication. An attacker sends a crafted HTTP POST request to the /goform/telnet endpoint with malicious payloads embedded in the request parameters. The handler function processes these parameters and passes them to a system shell, where injected commands execute with root privileges.

The attack can be conducted remotely against any Tenda AC15 router with the vulnerable firmware version that has its web management interface accessible to the attacker. This includes devices exposed directly to the internet or those accessible via compromised internal network positions.

For detailed technical analysis of the exploitation mechanism, refer to the GitHub IoT Vulnerability Documentation.

Detection Methods for CVE-2025-25632

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/telnet with unusual parameter values containing shell metacharacters
• Anomalous outbound connections from router management interface to unknown external IP addresses
• Unexplained configuration changes including modified DNS servers, firewall rules, or new user accounts
• Presence of unauthorized processes running on the router device

Detection Strategies

• Deploy network intrusion detection signatures to identify HTTP requests to /goform/telnet containing command injection patterns
• Monitor web server logs on network devices for requests to the vulnerable endpoint
• Implement network behavior analysis to detect unusual traffic patterns from router management interfaces
• Use vulnerability scanners to identify Tenda AC15 devices running firmware version 15.03.05.19

Monitoring Recommendations

• Enable comprehensive logging on Tenda AC15 devices if supported
• Monitor network traffic for unexpected telnet or reverse shell connections originating from router devices
• Implement egress filtering to alert on suspicious outbound connections from network infrastructure devices
• Regularly audit router configurations for unauthorized modifications

How to Mitigate CVE-2025-25632

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access from WAN interface immediately
• Place affected devices behind a firewall that blocks external access to management ports
• Monitor for any indicators of compromise on potentially exposed devices
• Consider replacing vulnerable devices if patches are unavailable

Patch Information

At the time of publication, no vendor security advisory or firmware patch has been released for this vulnerability. Affected organizations should monitor Tenda's official support channels for firmware updates addressing CVE-2025-25632. Technical details are available in the GitHub IoT Vulnerability Documentation.

Workarounds

• Disable remote web management access entirely on affected devices
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Use firewall rules to restrict access to /goform/telnet endpoint
• Deploy a reverse proxy with web application firewall capabilities to filter malicious requests
• Consider replacing affected devices with supported hardware from vendors with responsive security practices

# Example firewall rule to block external access to router management
# Adjust network interface and IP ranges for your environment
iptables -A INPUT -i eth0 -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP