CVE-2026-4554: Tenda F453 RCE Vulnerability

CVE-2026-4554 Overview

A command injection vulnerability has been discovered in Tenda F453 firmware version 1.0.0.3. The vulnerability exists in the FormWriteFacMac function within the /goform/WriteFacMac endpoint. By manipulating the mac argument, an attacker can inject arbitrary system commands that will be executed on the affected device. This vulnerability can be exploited remotely over the network, and public exploit code has been released.

Critical Impact

Remote attackers can execute arbitrary commands on vulnerable Tenda F453 routers by exploiting improper input validation in the mac parameter, potentially leading to complete device compromise.

Affected Products

• Tenda F453 firmware version 1.0.0.3

Discovery Timeline

• 2026-03-22 - CVE-2026-4554 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2026-4554

Vulnerability Analysis

This command injection vulnerability (CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component) affects the web management interface of Tenda F453 routers. The vulnerability resides in the FormWriteFacMac function, which handles requests to the /goform/WriteFacMac endpoint. When processing the mac parameter, the function fails to properly sanitize user input before passing it to system command execution functions.

The network-accessible nature of this vulnerability means that any attacker with network access to the router's management interface can potentially exploit it. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild.

Root Cause

The root cause is improper input validation in the FormWriteFacMac function. The mac argument is directly incorporated into system commands without adequate sanitization or escaping of shell metacharacters. This allows attackers to inject additional commands by including special characters such as semicolons, pipes, or backticks in the mac parameter value.

Attack Vector

The attack is conducted remotely over the network by sending a specially crafted HTTP request to the /goform/WriteFacMac endpoint. The attacker includes malicious shell commands within the mac parameter. When the vulnerable FormWriteFacMac function processes this input, the injected commands are executed with the privileges of the web server process, which typically runs as root on embedded devices like routers.

For detailed technical analysis and proof-of-concept information, refer to the GitHub Vulnerability Report.

Detection Methods for CVE-2026-4554

Indicators of Compromise

• Unusual HTTP POST requests to /goform/WriteFacMac containing shell metacharacters in the mac parameter
• Unexpected processes spawned by the web server process on the router
• Anomalous outbound network connections from the router to unknown external hosts
• Router configuration changes or new user accounts not created by administrators

Detection Strategies

• Monitor HTTP traffic for requests targeting /goform/WriteFacMac with suspicious mac parameter values containing characters like ;, |, $(), or backticks
• Implement network intrusion detection rules to identify command injection patterns in router management traffic
• Review router logs for unexpected command execution or authentication failures
• Deploy network monitoring to detect unusual traffic patterns from router devices

Monitoring Recommendations

• Enable logging on the router management interface if available
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Deploy intrusion detection/prevention systems (IDS/IPS) with signatures for command injection attacks
• Regularly audit network traffic to and from router management ports

How to Mitigate CVE-2026-4554

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access if not required
• Place the router management interface on a separate, isolated management VLAN
• Monitor for any suspicious activity targeting the /goform/WriteFacMac endpoint

Patch Information

No official patch information is currently available from Tenda. Users should monitor the Tenda official website for firmware updates addressing this vulnerability. Additional vulnerability details can be found in the VulDB entry #352381.

Workarounds

• Implement firewall rules to block external access to the router's management interface (typically port 80 or 443)
• Use access control lists (ACLs) to restrict management access to specific trusted IP addresses
• Consider deploying a web application firewall (WAF) in front of the management interface to filter malicious requests
• If possible, disable the affected /goform/WriteFacMac endpoint until a patch is available

# Example iptables rules to restrict management access
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP