CVE-2026-6137: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6137 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda F451 firmware version 1.0.0.7_cn_svn7958. The vulnerability exists in the fromAdvSetWan function within the /goform/AdvSetWan endpoint. By manipulating the wanmode or PPPOEPassword arguments, an attacker can trigger a buffer overflow condition that may lead to remote code execution or denial of service. The exploit is publicly available, increasing the risk of exploitation in the wild.

Critical Impact

Remote attackers with low privileges can exploit this stack-based buffer overflow to potentially execute arbitrary code or crash the affected device, compromising network security.

Affected Products

• Tenda F451 firmware version 1.0.0.7_cn_svn7958

Discovery Timeline

• April 13, 2026 - CVE-2026-6137 published to NVD
• April 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6137

Vulnerability Analysis

This vulnerability falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromAdvSetWan function in the Tenda F451 router firmware fails to properly validate the length of user-supplied input when processing the wanmode and PPPOEPassword parameters. When an attacker sends an overly long string to these parameters via the /goform/AdvSetWan endpoint, the function copies this data into a fixed-size stack buffer without bounds checking, resulting in a classic stack-based buffer overflow condition.

This type of vulnerability can allow attackers to overwrite critical stack data including saved return addresses, potentially redirecting program execution to attacker-controlled code. Given the embedded nature of router firmware, successful exploitation could grant complete control over the device.

Root Cause

The root cause is improper input validation and lack of boundary checking in the fromAdvSetWan function. The function uses unsafe string handling operations that do not verify the length of the wanmode and PPPOEPassword parameters before copying them to stack-allocated buffers. This violates secure coding practices for handling user-controllable input in memory-constrained embedded systems.

Attack Vector

The attack can be executed remotely over the network. An authenticated attacker with low privileges can send a crafted HTTP POST request to the /goform/AdvSetWan endpoint containing malicious values for the wanmode or PPPOEPassword parameters. The oversized input triggers the buffer overflow, potentially allowing the attacker to execute arbitrary code with the privileges of the web server process on the router.

The attack requires network access to the router's web management interface, which may be accessible from the local network or, if misconfigured, from the internet.

Detection Methods for CVE-2026-6137

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/AdvSetWan with unusually long wanmode or PPPOEPassword parameter values
• Router crashes or unexpected reboots that may indicate exploitation attempts
• Anomalous outbound network traffic from the router suggesting command and control communication
• Modified router configurations or unauthorized administrative accounts

Detection Strategies

• Implement network intrusion detection rules to monitor for HTTP requests to /goform/AdvSetWan containing parameters exceeding expected length thresholds
• Deploy web application firewall rules to block requests with oversized POST parameters targeting Tenda router endpoints
• Monitor router logs for repeated authentication failures or unusual access patterns to the web management interface
• Utilize SentinelOne Singularity to detect anomalous network behavior and potential lateral movement following router compromise

Monitoring Recommendations

• Enable logging on all network devices and centralize log collection for correlation and analysis
• Monitor network traffic for signs of exploitation attempts against IoT and embedded devices
• Implement network segmentation to limit exposure of router management interfaces
• Regularly audit device configurations for unauthorized changes

How to Mitigate CVE-2026-6137

Immediate Actions Required

• Restrict access to the router's web management interface to trusted networks and IP addresses only
• Disable remote management features if not required for operations
• Implement network segmentation to isolate vulnerable devices from critical network segments
• Monitor the Tenda Official Website for firmware updates addressing this vulnerability

Patch Information

No official patch has been released by Tenda at the time of publication. Organizations should monitor the VulDB entry and vendor channels for security updates. Additional technical details are available in the GitHub CVE Issue Discussion.

Workarounds

• Disable the WAN configuration interface if not actively needed for device management
• Implement access control lists (ACLs) on upstream network devices to restrict access to the router's management ports
• Consider replacing vulnerable devices with models from vendors with more responsive security update practices
• Deploy a network firewall or intrusion prevention system in front of the vulnerable device to filter malicious requests

# Example: Restrict access to router management interface via upstream firewall
# Block external access to common router management ports
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP