CVE-2026-3769: Tenda F453 Buffer Overflow Vulnerability

CVE-2026-3769 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda F453 wireless router firmware version 1.0.0.3. This vulnerability exists within the WrlclientSet function located in the /goform/WrlclientSet endpoint. The flaw is triggered through manipulation of the GO argument, which fails to properly validate input boundaries before copying data to a fixed-size stack buffer. Attackers can exploit this vulnerability remotely over the network to potentially achieve arbitrary code execution on affected devices.

Critical Impact

Remote attackers with low privileges can exploit this stack-based buffer overflow to potentially execute arbitrary code on the router, compromising network security and enabling further attacks on connected devices.

Affected Products

• Tenda F453 Firmware version 1.0.0.3
• Tenda F453 Hardware

Discovery Timeline

• 2026-03-08 - CVE-2026-3769 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-3769

Vulnerability Analysis

This vulnerability stems from improper memory bounds checking in the WrlclientSet function within the Tenda F453 router firmware. The function processes user-supplied input from the GO parameter without adequately validating the length of the input data. When an attacker submits a specially crafted request with an oversized GO parameter value, the function copies this data into a fixed-size buffer on the stack, causing a buffer overflow condition.

The attack surface is accessible via the network through the device's web management interface at the /goform/WrlclientSet endpoint. This remote attack vector significantly increases the risk, as attackers do not require physical access to the device. The vulnerability requires only low-level privileges to exploit, making it particularly dangerous in environments where multiple users have access to the router's administrative interface.

Upon successful exploitation, an attacker could overwrite critical stack memory structures including the return address pointer, enabling control flow hijacking and potentially achieving arbitrary code execution with the privileges of the router's web server process. This could lead to complete device compromise, enabling attackers to intercept network traffic, modify router configurations, or use the compromised device as a pivot point for further attacks within the network.

Root Cause

The root cause of this vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The WrlclientSet function in the Tenda F453 firmware lacks proper input validation and bounds checking when handling the GO parameter. The function allocates a fixed-size buffer on the stack and copies user-supplied data without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow pattern allows stack corruption when oversized input is provided.

Attack Vector

The vulnerability is exploitable remotely over the network. An attacker can craft a malicious HTTP request to the /goform/WrlclientSet endpoint with an oversized GO parameter. This triggers the stack-based buffer overflow condition, potentially allowing the attacker to overwrite the return address and redirect execution flow to attacker-controlled code. The exploit has been documented publicly, increasing the likelihood of exploitation attempts in the wild.

The attack mechanism involves sending a specially crafted POST request to the vulnerable endpoint containing a payload designed to overflow the stack buffer. The payload typically includes a large amount of data followed by shellcode or a ROP chain to achieve code execution. Additional technical details regarding the exploitation technique can be found in the GitHub Vulnerability Documentation.

Detection Methods for CVE-2026-3769

Indicators of Compromise

• Unusual HTTP POST requests to /goform/WrlclientSet with abnormally large GO parameter values
• Router crashes, unexpected reboots, or unresponsive web management interface
• Unauthorized configuration changes to the router settings
• Unexpected outbound connections from the router to unknown IP addresses

Detection Strategies

• Monitor web server logs for requests to /goform/WrlclientSet containing oversized parameters
• Implement network intrusion detection rules to identify buffer overflow exploitation patterns targeting Tenda devices
• Deploy anomaly-based detection to flag unusual parameter lengths in HTTP requests to router management interfaces
• Use firmware integrity verification to detect unauthorized modifications to the router's file system

Monitoring Recommendations

• Enable comprehensive logging on the router and forward logs to a centralized SIEM for analysis
• Monitor network traffic for suspicious activity originating from or targeting the router's IP address
• Implement network segmentation to isolate IoT devices and routers from critical network assets
• Conduct periodic firmware integrity checks to identify potential compromises

How to Mitigate CVE-2026-3769

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management if not required for operations
• Place the router behind a firewall that blocks external access to the /goform/ endpoints
• Monitor for firmware updates from Tenda and apply patches as soon as they become available

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Security Information page for security updates and firmware releases. Consider replacing affected devices with alternative products if patches are not made available in a timely manner.

For additional vulnerability details and tracking information, refer to VulDB #349747.

Workarounds

• Configure firewall rules to block external access to the router's web interface on ports 80 and 443
• Implement access control lists (ACLs) to restrict management interface access to specific trusted IP addresses
• Disable the web management interface entirely if an alternative management method (such as SSH or serial console) is available
• Deploy network monitoring to detect and alert on exploitation attempts targeting the vulnerable endpoint

# Example firewall rule to block external access to router management interface
# Apply to upstream firewall or edge device protecting the Tenda F453

# Block external access to web management ports
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 management access only from trusted admin subnet
iptables -A FORWARD -s <trusted_admin_subnet> -d <router_ip> -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -s <trusted_admin_subnet> -d <router_ip> -p tcp --dport 443 -j ACCEPT