CVE-2025-70802: Tenda G1 Auth Bypass Vulnerability

CVE-2025-70802 Overview

A hardcoded password vulnerability has been discovered in Tenda G1V3.1si Firmware V16.01.7.8 that allows attackers to gain root-level access to affected devices. The vulnerability exists in the /etc_ro/shadow file, which contains hardcoded credentials that can be exploited by attackers with local access to authenticate as the root user and gain complete control over the device.

Critical Impact

Attackers with local access can authenticate as root using hardcoded credentials, potentially compromising network infrastructure and gaining complete control over the affected Tenda router.

Affected Products

• Tenda G1V3.1si Firmware V16.01.7.8

Discovery Timeline

• 2026-03-10 - CVE-2025-70802 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2025-70802

Vulnerability Analysis

This vulnerability falls under CWE-259 (Use of Hard-coded Password), a critical security weakness commonly found in embedded devices and firmware. The Tenda G1V3.1si router contains static credentials embedded directly in the firmware's /etc_ro/shadow file. These hardcoded credentials cannot be changed by end users through normal configuration interfaces, leaving devices permanently vulnerable.

The local attack vector requires an attacker to have some form of access to the device, such as physical console access, SSH access to the local network, or access through another vulnerability that provides local shell access. Once an attacker obtains the hardcoded root password, they gain complete administrative control over the router.

Root Cause

The root cause of this vulnerability is the inclusion of static, unchangeable root credentials in the device firmware. The /etc_ro/shadow file contains password hashes that are identical across all devices running this firmware version. This represents a fundamental security design flaw where developers embedded credentials for debugging, manufacturing, or maintenance purposes without implementing proper credential management or removal before production release.

Attack Vector

The attack requires local access to the device. An attacker would need to extract the firmware image or gain shell access to read the /etc_ro/shadow file. Once obtained, the hardcoded root password can be recovered through offline password cracking or may already be documented in public vulnerability disclosures. With the root password, an attacker can authenticate via console, SSH, or other administrative interfaces to gain full control of the router.

The vulnerability mechanism involves reading the /etc_ro/shadow file which contains the root user's password hash. This hash is static across all devices running the affected firmware version. Security researchers have documented this vulnerability in the GitHub Security Report. Once the hash is obtained, standard password cracking tools can be used to recover the plaintext password.

Detection Methods for CVE-2025-70802

Indicators of Compromise

• Unexpected root login sessions or authentication attempts on the affected device
• Unauthorized configuration changes to router settings, firewall rules, or DNS configurations
• Suspicious outbound connections from the router to unknown external IP addresses
• Modification of system files or installation of unauthorized services

Detection Strategies

• Monitor authentication logs for successful root logins, especially from unexpected sources or at unusual times
• Implement network monitoring to detect anomalous traffic patterns originating from the router
• Deploy file integrity monitoring on critical system files if the device supports such capabilities
• Review SSH and console access logs for unauthorized access attempts

Monitoring Recommendations

• Enable and centralize logging from all network devices including Tenda routers
• Configure alerts for any root-level authentication events
• Implement network segmentation to limit lateral movement if a router is compromised
• Periodically audit device configurations for unauthorized changes

How to Mitigate CVE-2025-70802

Immediate Actions Required

• Restrict physical access to affected Tenda G1V3.1si devices
• Disable unnecessary remote management services (SSH, Telnet, web management) from untrusted networks
• Implement network segmentation to isolate affected devices from critical network segments
• Monitor the Tenda Official Website for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no official patch has been released by Tenda to address this vulnerability. Organizations using affected devices should contact Tenda support directly and monitor their official channels for security advisories. Consider replacing affected devices with hardware from vendors that have resolved this vulnerability if a patch is not released in a timely manner.

Workarounds

• Restrict management interface access to trusted internal IP addresses only using firewall rules
• Disable remote administration features if not required for operations
• Place affected routers behind additional network security controls such as firewalls or intrusion prevention systems
• Consider replacing vulnerable devices with alternative products that do not contain hardcoded credentials

Access restrictions can be implemented at the network level to limit which hosts can reach the router's administrative interfaces. Configure upstream firewalls or access control lists to permit management traffic only from authorized administrator workstations. Additionally, disabling unused services such as Telnet or SSH on the device reduces the attack surface for credential-based attacks.