CVE-2025-70798: Tenda i24 Auth Bypass Vulnerability

CVE-2025-70798 Overview

A critical hardcoded password vulnerability has been discovered in Tenda i24V3.0si Firmware V3.0.0.5. The vulnerability exists within the /etc_ro/shadow file, which contains hardcoded credentials that allow attackers with local access to authenticate as the root user. This type of vulnerability (CWE-259: Use of Hard-coded Password) represents a severe security flaw in embedded device firmware, as it cannot be mitigated through standard password management practices and provides persistent unauthorized access to the device.

Critical Impact

Attackers who gain local access to vulnerable Tenda i24V3 devices can leverage hardcoded credentials in /etc_ro/shadow to obtain full root-level access, enabling complete device compromise, network pivoting, and potential lateral movement across enterprise environments.

Affected Products

• Tenda i24V3.0si Firmware V3.0.0.5
• Tenda i24V3 devices running affected firmware versions

Discovery Timeline

• 2026-03-10 - CVE CVE-2025-70798 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2025-70798

Vulnerability Analysis

This vulnerability stems from the insecure practice of embedding static credentials directly within the firmware's read-only filesystem. The /etc_ro/shadow file, which stores password hashes on Unix-like systems, contains a hardcoded password for the root account. Unlike standard /etc/shadow configurations that can be modified by system administrators, the _ro suffix indicates this file resides in a read-only partition, making credential rotation impossible without a complete firmware update.

The hardcoded nature of these credentials means that every deployed Tenda i24V3.0si device running firmware V3.0.0.5 shares identical root access credentials. Once these credentials are extracted from a single device—either through firmware analysis, physical access, or other means—all devices running the same firmware version become vulnerable to root-level compromise.

Root Cause

The root cause of this vulnerability is CWE-259 (Use of Hard-coded Password). During the firmware development process, static credentials were embedded in the /etc_ro/shadow file and compiled into the read-only firmware image. This practice violates fundamental secure development principles, which mandate the use of unique, randomly generated credentials that can be changed by end users during initial device configuration.

The firmware's architecture compounds this issue by storing the shadow file in a read-only partition (/etc_ro/), preventing administrators from implementing credential rotation as a security control. This design decision transforms what might otherwise be a configuration weakness into a permanent security flaw that persists across all device deployments.

Attack Vector

The attack requires local access to the device, which can be achieved through several vectors:

The attacker must first gain access to the device's command-line interface, either through physical console access, SSH, Telnet, or by exploiting another vulnerability that provides shell access. Once command-line access is obtained, the attacker can extract the hardcoded password hash from /etc_ro/shadow.

The extracted hash can then be subjected to offline password cracking using tools like John the Ripper or Hashcat. Given that the password is hardcoded across all devices, it is likely to be a weak or commonly used credential that can be cracked relatively quickly. Alternatively, if the firmware has been publicly analyzed, the plaintext password may already be available through security research disclosures.

With the root password in hand, the attacker can authenticate as the root user, gaining complete administrative control over the device. This access enables modification of device configurations, installation of persistent backdoors, interception of network traffic, and use of the device as a pivot point for further network intrusion.

Detection Methods for CVE-2025-70798

Indicators of Compromise

• Unexpected root-level login attempts or successful authentications on Tenda i24V3 devices
• Modified device configurations that were not authorized by administrators
• Presence of unauthorized user accounts or SSH keys on the device
• Unusual outbound network connections originating from the affected device
• Changes to firewall rules or network routing on the device

Detection Strategies

• Monitor authentication logs for root login attempts, particularly from unexpected sources or at unusual times
• Implement network segmentation to isolate IoT devices and detect lateral movement attempts
• Deploy network monitoring to identify command-and-control communications from embedded devices
• Conduct periodic firmware integrity checks to detect unauthorized modifications

Monitoring Recommendations

• Enable verbose logging on all network infrastructure devices and forward logs to a centralized SIEM
• Implement anomaly detection for device behavior patterns, including network traffic and resource utilization
• Regularly audit device configurations against known-good baselines
• Monitor for firmware analysis attempts on network shares or suspicious downloads of device firmware

How to Mitigate CVE-2025-70798

Immediate Actions Required

• Identify all Tenda i24V3.0si devices running Firmware V3.0.0.5 in your environment
• Isolate affected devices on a separate network segment with strict access controls
• Restrict physical and network access to affected devices to authorized personnel only
• Monitor affected devices for signs of compromise while awaiting a firmware update from the vendor

Patch Information

At the time of publication, no official security patch has been released by Tenda to address this vulnerability. Administrators should monitor the Tenda Official Website for firmware updates that address this security issue. Additional technical details about this vulnerability are available in the GitHub Vulnerability Report.

Workarounds

• Implement network segmentation to isolate affected devices from sensitive network resources
• Disable remote management interfaces (SSH, Telnet, web interface) if not required for operations
• Deploy firewall rules to restrict access to device management interfaces to specific trusted IP addresses
• Consider replacing affected devices with alternative products that follow secure credential management practices
• Implement network access control (NAC) to limit which systems can communicate with affected devices

# Example: Firewall rules to restrict management access
# Restrict SSH access to Tenda devices from trusted management VLAN only
iptables -A INPUT -p tcp --dport 22 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j DROP

# Restrict web interface access
iptables -A INPUT -p tcp --dport 80 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP

# Restrict Telnet access (recommended: disable Telnet entirely)
iptables -A INPUT -p tcp --dport 23 -j DROP