CVE-2026-3727: Tenda F453 Firmware Buffer Overflow Flaw

CVE-2026-3727 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda F453 firmware version 1.0.0.3. This vulnerability affects the function sub_3C6C0 within the /goform/QuickIndex endpoint. The manipulation of the mit_linktype or PPPOEPassword arguments results in a stack-based buffer overflow condition that can be exploited remotely by an authenticated attacker. The exploit has been made public, increasing the risk of active exploitation attempts against vulnerable devices.

Critical Impact

This stack-based buffer overflow vulnerability allows remote attackers with low privileges to potentially achieve full compromise of the affected Tenda F453 router, impacting confidentiality, integrity, and availability of the device and connected network segments.

Affected Products

• Tenda F453 Firmware version 1.0.0.3
• Tenda F453 Hardware

Discovery Timeline

• 2026-03-08 - CVE-2026-3727 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-3727

Vulnerability Analysis

This vulnerability is classified as a stack-based buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the sub_3C6C0 function, which is responsible for processing HTTP requests sent to the /goform/QuickIndex endpoint on the router's web management interface.

When user-supplied input is provided through the mit_linktype or PPPOEPassword parameters, the function fails to properly validate the length of the input before copying it to a fixed-size stack buffer. This oversight allows an attacker to supply an oversized input string that overwrites adjacent memory on the stack, potentially corrupting the function's return address and other critical data structures.

The network-based attack vector with low complexity and no user interaction required makes this vulnerability particularly concerning for exposed devices. An authenticated attacker can exploit this flaw remotely to potentially execute arbitrary code with elevated privileges on the affected router.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the sub_3C6C0 function when handling the mit_linktype and PPPOEPassword parameters. The firmware fails to validate the length of user-supplied input before copying it into a stack-allocated buffer, leading to a classic stack-based buffer overflow condition. This represents a fundamental input validation failure common in embedded device firmware where memory safety checks may be omitted for performance or resource constraints.

Attack Vector

The attack can be launched remotely over the network against the router's web management interface. An attacker with valid credentials (low privilege requirement) can craft a malicious HTTP POST request to the /goform/QuickIndex endpoint containing an oversized value for either the mit_linktype or PPPOEPassword parameter.

The exploitation process involves:

1. Authenticating to the router's web management interface
2. Crafting an HTTP POST request to /goform/QuickIndex
3. Including a specially crafted oversized payload in the vulnerable parameters
4. The oversized input overwrites the stack, potentially enabling arbitrary code execution

For detailed technical analysis and proof-of-concept information, refer to the GitHub Vulnerability Document maintained by the vulnerability researchers.

Detection Methods for CVE-2026-3727

Indicators of Compromise

• Unusual or malformed HTTP POST requests to /goform/QuickIndex endpoint with abnormally long mit_linktype or PPPOEPassword parameter values
• Unexpected router reboots or crashes that may indicate exploitation attempts or failed buffer overflow attacks
• Anomalous outbound network connections from the router to unknown external IP addresses
• Changes to router configuration or firmware that were not authorized by administrators

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests to /goform/QuickIndex containing oversized parameter values exceeding expected buffer sizes
• Monitor router syslog and crash logs for evidence of memory corruption or unexpected service restarts
• Deploy web application firewall (WAF) rules on network segments to filter requests with suspicious payload lengths targeting Tenda router endpoints
• Review authentication logs for unusual access patterns to the router's management interface

Monitoring Recommendations

• Enable verbose logging on network perimeter devices to capture traffic destined for Tenda router management interfaces
• Implement real-time alerting for HTTP requests to Tenda router endpoints containing payload sizes exceeding normal operational parameters
• Establish baseline behavior for router management access and alert on deviations
• Consider network segmentation to isolate router management interfaces from untrusted network segments

How to Mitigate CVE-2026-3727

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only using firewall rules or access control lists
• Disable remote management access if not required for operational purposes
• Ensure strong, unique credentials are configured for the router's administrative account
• Monitor for firmware updates from Tenda that address this vulnerability
• Consider replacing affected devices if patches are not available and the risk is unacceptable

Patch Information

At the time of publication, no official patch information has been released by Tenda for this vulnerability. Administrators should monitor the Tenda Security Homepage for security updates and firmware releases. Additional vulnerability details can be found at VulDB #349705.

Workarounds

• Implement network-level access controls to restrict management interface access to trusted administrator workstations only
• Place the router's management interface on a dedicated management VLAN isolated from general network traffic
• Deploy an upstream firewall or reverse proxy to filter and sanitize requests to the /goform/QuickIndex endpoint
• Disable the web management interface entirely if command-line or alternative management methods are available and sufficient
• Consider implementing additional authentication mechanisms such as VPN access requirements for router management

# Example: Restrict management access via iptables on upstream device
# Allow management access only from trusted admin subnet
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -s 192.168.10.0/24 -j ACCEPT
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP

# Block external access to vulnerable endpoint
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -m string --string "/goform/QuickIndex" --algo bm -j LOG --log-prefix "CVE-2026-3727 Attempt: "
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -m string --string "/goform/QuickIndex" --algo bm -s !192.168.10.0/24 -j DROP