CVE-2025-45042: Tenda AC9 Firmware RCE Vulnerability

CVE-2025-45042 Overview

CVE-2025-45042 is a command injection vulnerability discovered in the Tenda AC9 wireless router running firmware version 15.03.05.14. The vulnerability exists in the Telnet function of the device, allowing attackers to inject and execute arbitrary system commands. This is a critical firmware vulnerability affecting IoT network infrastructure devices commonly deployed in home and small business environments.

Critical Impact

This command injection vulnerability enables unauthenticated remote attackers to execute arbitrary commands on the affected Tenda AC9 router, potentially leading to complete device compromise, network infiltration, and use of the router as a pivot point for further attacks.

Affected Products

• Tenda AC9 Firmware version 15.03.05.14
• Tenda AC9 Hardware version 1.0
• Tenda AC9 wireless routers with vulnerable firmware

Discovery Timeline

• 2025-05-05 - CVE-2025-45042 published to NVD
• 2025-05-07 - Last updated in NVD database

Technical Details for CVE-2025-45042

Vulnerability Analysis

This vulnerability is classified under CWE-77 (Improper Neutralization of Special Elements used in a Command) and CWE-78 (Improper Neutralization of Special Elements used in an OS Command). The Telnet function in the Tenda AC9 firmware fails to properly sanitize user-supplied input before incorporating it into system commands executed by the underlying operating system.

The vulnerability can be exploited remotely over the network without requiring any authentication or user interaction. Successful exploitation grants the attacker the same privileges as the process handling the Telnet function, which typically runs with elevated privileges on embedded devices like routers.

Root Cause

The root cause of CVE-2025-45042 lies in improper input validation within the Telnet functionality of the Tenda AC9 firmware. When processing user input, the firmware directly passes unsanitized data to system command execution functions without filtering shell metacharacters or command separators. This allows attackers to break out of the intended command context and inject arbitrary commands that will be executed by the router's operating system.

Attack Vector

The attack vector is network-based, enabling remote exploitation. An attacker can craft malicious requests to the Telnet service containing command injection payloads. These payloads leverage shell metacharacters such as semicolons, pipes, or backticks to append or inject additional commands that the router will execute.

The vulnerability mechanism involves the Telnet function accepting user input that is subsequently passed to a system shell without proper sanitization. Attackers can exploit this by including shell metacharacters and arbitrary commands within their input, which are then interpreted and executed by the underlying operating system. For detailed technical analysis and proof-of-concept information, refer to the GitHub PoC Repository.

Detection Methods for CVE-2025-45042

Indicators of Compromise

• Unusual outbound network connections originating from the router to unknown external IP addresses
• Unexpected processes running on the router that are not part of standard firmware operations
• Modified configuration files or presence of unauthorized user accounts on the device
• Abnormal Telnet service behavior or crash logs indicating exploitation attempts

Detection Strategies

• Monitor network traffic for suspicious Telnet communications containing shell metacharacters or unusual command patterns
• Implement network-based intrusion detection rules to identify command injection payload signatures targeting Tenda devices
• Deploy honeypot systems configured as vulnerable Tenda routers to capture exploitation attempts
• Analyze router logs for authentication anomalies and unexpected command execution patterns

Monitoring Recommendations

• Enable comprehensive logging on network firewalls to track all Telnet traffic to and from Tenda devices
• Configure SIEM systems to alert on traffic patterns indicative of command injection attempts
• Regularly audit router configurations and compare against known-good baselines
• Monitor for firmware integrity changes that may indicate post-exploitation modifications

How to Mitigate CVE-2025-45042

Immediate Actions Required

• Disable the Telnet service on the Tenda AC9 router if not required for legitimate operations
• Restrict network access to the router's management interfaces using firewall rules
• Place the affected router behind a network firewall and limit exposure to untrusted networks
• Monitor vendor communications for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no official vendor patch has been released for CVE-2025-45042. Tenda has not published a security advisory addressing this vulnerability. Organizations should monitor the Tenda support website for firmware updates and apply patches as soon as they become available. Until a patch is released, implementing the workarounds below is strongly recommended.

Workarounds

• Disable the Telnet service entirely on the affected Tenda AC9 router to eliminate the attack surface
• Implement network segmentation to isolate the vulnerable router from critical network assets
• Configure access control lists (ACLs) to restrict Telnet access to trusted management IP addresses only
• Consider replacing the affected device with an alternative router that does not contain this vulnerability

# Example: Firewall rule to block external Telnet access to Tenda router
# Adjust interface and IP addresses as appropriate for your environment
iptables -A INPUT -p tcp --dport 23 -s ! 192.168.1.0/24 -j DROP
iptables -A FORWARD -p tcp --dport 23 -d 192.168.1.1 -j DROP