CVE-2026-4492: Tenda A18 Pro Buffer Overflow Vulnerability

CVE-2026-4492 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda A18 Pro router firmware version 02.03.02.28. The vulnerability exists in the set_qosMib_list function within the /goform/formSetQosBand file. An attacker can exploit this vulnerability by manipulating the list argument, leading to memory corruption that could potentially allow remote code execution or denial of service.

Critical Impact

This stack-based buffer overflow vulnerability allows remote attackers with low privileges to potentially execute arbitrary code or crash the affected device, compromising network security and availability.

Affected Products

• Tenda A18 Pro firmware version 02.03.02.28

Discovery Timeline

• 2026-03-20 - CVE-2026-4492 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-4492

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The affected function set_qosMib_list fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer. This oversight allows an attacker to provide an oversized list argument that exceeds the buffer capacity, overwriting adjacent memory on the stack including potentially critical control flow data such as return addresses and saved frame pointers.

The vulnerability is remotely exploitable over the network and requires only low-level privileges to trigger, making it particularly concerning for consumer and small business network environments where Tenda routers are commonly deployed.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the set_qosMib_list function. When processing QoS (Quality of Service) band configuration data submitted through the web interface at /goform/formSetQosBand, the function copies the list parameter into a stack-allocated buffer without verifying that the input length does not exceed the buffer size. This classic buffer overflow pattern is common in embedded device firmware where memory-safe programming practices are not consistently applied.

Attack Vector

The attack vector is network-based, targeting the router's web management interface. An authenticated attacker with low privileges can submit a specially crafted HTTP request to the /goform/formSetQosBand endpoint with a malicious list parameter containing an oversized payload. The vulnerable function processes this input without adequate validation, causing the stack buffer to overflow.

Upon successful exploitation, an attacker may achieve:

• Arbitrary code execution with the privileges of the web server process
• Denial of service through device crash or hang
• Complete compromise of the router and potentially the entire network

The exploit details have been publicly disclosed, as documented in the GitHub Issue Discussion. Additional technical information is available through VulDB #352018.

Detection Methods for CVE-2026-4492

Indicators of Compromise

• Unusual HTTP POST requests to /goform/formSetQosBand containing abnormally long list parameter values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Unexpected processes or network connections originating from the router device
• Modified router configuration or firmware without administrator action

Detection Strategies

• Monitor web server logs for requests to /goform/formSetQosBand with unusually large payloads
• Implement network intrusion detection rules to identify buffer overflow patterns in HTTP traffic to Tenda devices
• Deploy SentinelOne Singularity to detect exploitation attempts and anomalous behavior on network endpoints
• Establish baseline behavior for router management traffic and alert on deviations

Monitoring Recommendations

• Enable verbose logging on the Tenda A18 Pro if available and forward logs to a SIEM solution
• Monitor network traffic to and from the router's management interface for anomalies
• Implement automated firmware version checks to identify vulnerable deployments
• Configure network segmentation to isolate IoT and network infrastructure devices

How to Mitigate CVE-2026-4492

Immediate Actions Required

• Check the Tenda Official Website for firmware updates addressing this vulnerability
• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management if not required for operations
• Implement strong authentication and access controls for administrative access
• Consider replacing affected devices if no patch is available

Patch Information

At the time of publication, vendor patch information was not available in the CVE data. Administrators should monitor the Tenda Official Website for security advisories and firmware updates. Additional vulnerability details can be found through VulDB Submission #773682.

Workarounds

• Disable the web management interface and use alternative management methods if available
• Place the router behind a firewall that restricts access to management ports
• Implement network-level access controls to limit who can reach the router's management interface
• Monitor and log all access attempts to the web interface for security review
• Consider network segmentation to limit the blast radius if the device is compromised