CVE-2026-2910: Tenda HG9 Buffer Overflow Vulnerability

CVE-2026-2910 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda HG9 routers running firmware version 300001138. This vulnerability exists in the /boaform/formPing6 endpoint and can be exploited by manipulating the pingAddr argument. Remote attackers with low-level privileges can leverage this flaw to potentially execute arbitrary code or cause denial of service conditions on affected devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to gain unauthorized control over Tenda HG9 routers, potentially compromising network infrastructure and enabling further attacks on connected devices.

Affected Products

• Tenda HG9 Firmware version 300001138
• Tenda HG9 Hardware devices running vulnerable firmware

Discovery Timeline

• 2026-02-22 - CVE-2026-2910 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2026-2910

Vulnerability Analysis

This vulnerability affects the ping functionality within the Tenda HG9 router's web management interface. The vulnerable endpoint /boaform/formPing6 processes user-supplied input through the pingAddr parameter without adequate boundary checks. When an attacker provides an oversized or specially crafted input value, the application fails to properly validate the input length before copying it to a fixed-size stack buffer.

The flaw is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), indicating that the vulnerable code performs memory operations that can exceed allocated buffer boundaries. Successful exploitation requires network access and low-level authentication privileges, though no user interaction is needed.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the ping functionality handler. The pingAddr parameter accepts user input that is processed without proper bounds checking before being copied to a stack-allocated buffer. This classic buffer overflow pattern occurs when:

1. The application allocates a fixed-size buffer on the stack for the ping address
2. User input from the pingAddr parameter is copied to this buffer
3. No validation ensures the input length does not exceed the buffer size
4. An oversized input overwrites adjacent stack memory, including return addresses

Attack Vector

The attack can be executed remotely over the network. An authenticated attacker with low privileges can send a malicious HTTP request to the /boaform/formPing6 endpoint with a crafted pingAddr parameter value designed to overflow the stack buffer. The exploit has been publicly disclosed, increasing the risk of active exploitation.

The attack flow involves:

1. Attacker authenticates to the router's web interface with low-level credentials
2. Attacker sends a POST request to /boaform/formPing6 with an oversized pingAddr value
3. The vulnerable code copies the malicious input without bounds checking
4. Stack corruption occurs, potentially allowing control flow hijacking or denial of service

Technical details and proof-of-concept information can be found in the GitHub Issue Discussion and VulDB entry #347219.

Detection Methods for CVE-2026-2910

Indicators of Compromise

• Unusual HTTP POST requests to /boaform/formPing6 with abnormally long pingAddr parameter values
• Router crashes or unexpected reboots coinciding with web interface access
• Memory corruption errors in device logs related to the ping functionality
• Anomalous network traffic patterns originating from the router

Detection Strategies

• Deploy network intrusion detection rules to identify HTTP requests containing oversized payloads targeting /boaform/formPing6
• Monitor web server access logs for suspicious POST requests with unusually large parameter values
• Implement application-layer firewall rules to limit input sizes for form submissions to the router interface
• Use network traffic analysis to detect exploitation attempts against Tenda router management interfaces

Monitoring Recommendations

• Enable logging on all network traffic to and from Tenda HG9 device management interfaces
• Configure alerts for repeated authentication attempts followed by requests to the vulnerable endpoint
• Monitor for unexpected device behavior such as crashes, reboots, or configuration changes
• Implement network segmentation to limit management interface exposure

How to Mitigate CVE-2026-2910

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management capabilities if not required for operations
• Implement network segmentation to isolate the router management interface from untrusted networks
• Monitor for updated firmware from Tenda that addresses this vulnerability

Patch Information

At the time of publication, no official patch has been confirmed from Tenda. Organizations should monitor the Tenda Security Resource page for firmware updates that address this vulnerability. Check the VulDB entry and GitHub Issue Discussion for the latest remediation information.

Workarounds

• Implement access control lists (ACLs) to restrict web interface access to authorized administrators only
• Deploy a web application firewall (WAF) to filter malicious requests targeting the vulnerable endpoint
• Disable the ping6 functionality if not operationally required
• Consider replacing affected devices with alternatives that receive timely security updates

# Example: Restrict management interface access via iptables (on upstream device)
# Block external access to router management interface
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -j DROP

# Allow only trusted management IPs
iptables -I FORWARD -s <trusted_admin_ip> -d <router_ip> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s <trusted_admin_ip> -d <router_ip> -p tcp --dport 443 -j ACCEPT