CVE-2025-46627: Tenda RX2 Pro Auth Bypass Vulnerability

CVE-2025-46627 Overview

CVE-2025-46627 is a weak credentials vulnerability affecting the Tenda RX2 Pro router running firmware version 16.03.30.14. This security flaw allows an unauthenticated attacker to authenticate to the telnet service by calculating the root password based on easily-obtained device information. Specifically, the password is derived from the last two digits/octets of the device's MAC address, making it trivial for attackers with network access to gain root-level access to the device.

Critical Impact

Unauthenticated attackers can gain root access to affected Tenda RX2 Pro routers by simply knowing or discovering the device's MAC address, enabling complete device compromise and potential network pivot attacks.

Affected Products

• Tenda RX2 Pro Firmware version 16.03.30.14
• Tenda RX2 Pro hardware devices
• tenda rx2_pro_firmware

Discovery Timeline

• 2025-05-01 - CVE-2025-46627 published to NVD
• 2025-05-27 - Last updated in NVD database

Technical Details for CVE-2025-46627

Vulnerability Analysis

This vulnerability represents a fundamental design flaw in the Tenda RX2 Pro's authentication mechanism. The device uses a predictable password generation scheme for its telnet service, where the root password is calculated based on the device's MAC address—specifically the last two octets. Since MAC addresses are broadcast in network traffic and can be easily discovered through network scanning or physical access to the device, this creates a trivial authentication bypass scenario.

The attack requires no prior authentication and can be executed remotely over the network. An attacker who successfully exploits this vulnerability gains high-level confidentiality access to the device, with some ability to modify system configurations. This type of insecure credential implementation (CWE-922: Insecure Storage of Sensitive Information) represents a common but critical flaw in IoT and embedded device firmware.

Root Cause

The root cause of this vulnerability lies in the insecure design decision to generate root credentials using predictable, publicly-discoverable information. Rather than implementing proper credential management with unique, randomly-generated passwords or proper key-based authentication, the firmware developers chose to derive passwords from the MAC address. This approach assumes the MAC address would remain private, which is fundamentally incorrect given how network protocols operate.

Attack Vector

The attack vector is network-based and requires no user interaction or prior privileges. An attacker can exploit this vulnerability through the following general approach:

1. Discover the target Tenda RX2 Pro device on the network
2. Obtain the device's MAC address through network scanning or ARP traffic analysis
3. Extract the last two octets of the MAC address
4. Calculate the root password using the known algorithm
5. Connect to the telnet service and authenticate as root using the calculated password

The vulnerability can be exploited without any authenticated access, making it particularly dangerous in environments where the router's management interface is accessible from untrusted networks.

For detailed technical information about the password calculation method, refer to the Uturn Blog CVE-2025-46627 Writeup.

Detection Methods for CVE-2025-46627

Indicators of Compromise

• Unexpected telnet connections to port 23 on the Tenda RX2 Pro device
• Successful root authentication events from external or unexpected IP addresses
• Configuration changes or firmware modifications without authorized administrator action
• Unusual network traffic originating from the router indicating potential lateral movement

Detection Strategies

• Monitor network traffic for telnet connection attempts (TCP port 23) to Tenda RX2 Pro devices
• Implement network segmentation to isolate IoT devices and monitor cross-segment communication
• Deploy network intrusion detection systems (IDS) with rules for detecting telnet brute-force or successful authentication patterns
• Conduct regular asset inventory audits to identify vulnerable Tenda RX2 Pro devices running firmware 16.03.30.14

Monitoring Recommendations

• Enable logging on network firewalls and switches to track telnet traffic to embedded devices
• Implement SIEM alerts for any telnet authentication activity on IoT network segments
• Regularly review router logs for authentication events if accessible through the web interface
• Consider deploying network access control (NAC) solutions to restrict which devices can communicate with network infrastructure

How to Mitigate CVE-2025-46627

Immediate Actions Required

• Disable telnet service on affected Tenda RX2 Pro devices if not required for operations
• Implement network segmentation to isolate vulnerable routers from untrusted networks
• Block external access to telnet (port 23) on affected devices using firewall rules
• Monitor the Tenda Official Website for firmware updates addressing this vulnerability

Patch Information

At the time of this publication, no official patch from Tenda has been confirmed for this vulnerability. Organizations should monitor the vendor's security advisories and firmware release notes for updates addressing CVE-2025-46627. Until a patch is available, implementing the workarounds listed below is critical for reducing exposure.

Workarounds

• Disable the telnet service entirely through the router's administration interface if the feature exists
• Implement strict firewall rules blocking all telnet traffic (TCP port 23) to and from the affected device
• Place the router behind a VPN or additional firewall layer to limit exposure to trusted networks only
• Consider replacing the device with alternative hardware that implements proper credential management

# Configuration example - Block telnet access at network firewall
# Example iptables rules for upstream firewall protecting Tenda device

# Block external telnet access to the Tenda RX2 Pro
iptables -A FORWARD -d <TENDA_IP> -p tcp --dport 23 -j DROP

# Log any telnet connection attempts for monitoring
iptables -A FORWARD -d <TENDA_IP> -p tcp --dport 23 -j LOG --log-prefix "TELNET_BLOCKED: "