CVE-2026-6989: Tenda F453 Firmware RCE Vulnerability

CVE-2026-6989 Overview

A command injection vulnerability has been identified in Tenda F453 wireless routers running firmware versions up to 1.0.0.3. The vulnerability exists in the TendaTelnet function within the /goform/telnet endpoint of the Telnet Service component. This flaw allows authenticated attackers to inject and execute arbitrary system commands remotely on the affected device.

Critical Impact

Successful exploitation of this command injection vulnerability could allow attackers to gain unauthorized access to the router, execute arbitrary commands, and potentially compromise the entire network infrastructure connected to the device.

Affected Products

• Tenda F453 Firmware version 1.0.0.3 and earlier
• Tenda F453 Hardware devices

Discovery Timeline

• 2026-04-25 - CVE-2026-6989 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-6989

Vulnerability Analysis

This vulnerability is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly referred to as Injection. The flaw resides in the Telnet Service component of the Tenda F453 router firmware, specifically within the TendaTelnet function accessible through the /goform/telnet web interface endpoint.

The vulnerability allows an authenticated attacker with network access to craft malicious HTTP requests to the vulnerable endpoint. When user-supplied input is passed to the TendaTelnet function, insufficient input validation and sanitization allows command metacharacters to be interpreted by the underlying system shell. This enables command injection attacks where attacker-controlled commands are executed with the privileges of the web service process.

The attack can be launched remotely over the network, and proof-of-concept exploit information has been publicly disclosed, increasing the risk of exploitation in the wild. Organizations using affected Tenda F453 devices should prioritize assessment and remediation.

Root Cause

The root cause of this vulnerability is improper input validation in the TendaTelnet function. User-supplied parameters passed to the /goform/telnet endpoint are not adequately sanitized before being used in system command execution contexts. This allows shell metacharacters such as semicolons, pipes, and backticks to break out of intended command boundaries and execute arbitrary attacker-supplied commands.

Attack Vector

The attack is network-based and requires low-privilege authenticated access to the router's web management interface. An attacker can exploit this vulnerability by:

1. Gaining authenticated access to the Tenda F453 router's web interface
2. Crafting a malicious HTTP request to the /goform/telnet endpoint
3. Injecting shell command metacharacters along with malicious commands in the vulnerable parameter
4. The injected commands are executed by the router's operating system

The vulnerability allows injection of arbitrary system commands that could be used to establish persistent access, modify router configurations, intercept network traffic, or pivot to attack other devices on the network.

Detection Methods for CVE-2026-6989

Indicators of Compromise

• Unexpected HTTP requests to /goform/telnet endpoint containing shell metacharacters (;, |, `, $())
• Unusual process execution on the router device
• Unauthorized configuration changes to the Tenda F453 router
• Network traffic anomalies suggesting command and control communication originating from the router

Detection Strategies

• Monitor web server logs for suspicious requests to /goform/telnet containing injection patterns
• Implement network intrusion detection rules to identify command injection attempts targeting Tenda devices
• Deploy SentinelOne Singularity to detect and block exploitation attempts and post-exploitation activities
• Utilize IoT security monitoring solutions to baseline normal router behavior and alert on deviations

Monitoring Recommendations

• Enable logging on network security appliances to capture traffic to and from Tenda F453 devices
• Regularly review router access logs for unauthorized authentication attempts
• Configure alerts for any access to the /goform/telnet endpoint from untrusted sources
• Monitor for firmware modification attempts or unexpected outbound connections from router IP addresses

How to Mitigate CVE-2026-6989

Immediate Actions Required

• Restrict network access to the Tenda F453 web management interface to trusted administrative hosts only
• Disable remote administration features if not required for operations
• Implement network segmentation to isolate affected devices from critical network assets
• Consider replacing affected devices with alternative hardware from vendors with better security track records

Patch Information

At the time of this publication, no official security patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for firmware updates addressing CVE-2026-6989. Additional technical details can be found in the VulDB Entry #359541 and the GitHub Issue on CVE.

Workarounds

• Implement firewall rules to block external access to the router's web management interface on all affected Tenda F453 devices
• Deploy a Web Application Firewall (WAF) or reverse proxy with command injection detection rules in front of the management interface
• Disable the Telnet service entirely if it is not required for operations
• Use strong, unique credentials for router administration and enable multi-factor authentication if supported

# Example firewall rules to restrict management access (iptables)
# Allow management access only from trusted admin workstation
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP

# Block external access to management interface
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP