CVE-2026-5683: Tenda CX12L Buffer Overflow Vulnerability

CVE-2026-5683 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda CX12L router firmware version 16.03.53.12. The vulnerability exists in the fromP2pListFilter function within the /goform/P2pListFilter endpoint. An attacker with access to the adjacent network can exploit this vulnerability by manipulating the page argument, potentially leading to memory corruption, denial of service, or arbitrary code execution on the affected device.

Critical Impact

Attackers on the local network can exploit this buffer overflow vulnerability to compromise router integrity, potentially allowing network traffic interception, device denial of service, or further lateral movement within the network.

Affected Products

• Tenda CX12L Router - Firmware version 16.03.53.12

Discovery Timeline

• 2026-04-06 - CVE-2026-5683 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-5683

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which encompasses buffer overflow vulnerabilities where operations are performed outside the intended memory boundaries.

The vulnerable function fromP2pListFilter fails to properly validate the length of user-supplied input passed through the page parameter. When an attacker submits a specially crafted request with an oversized value for this parameter, the function writes data beyond the allocated stack buffer boundaries. This memory corruption can overwrite adjacent stack variables, saved return addresses, or other critical data structures.

The attack requires access to the adjacent network (local network segment), meaning the attacker must be connected to the same network as the vulnerable device. This is typical for router vulnerabilities where the management interface is accessible within the LAN.

Root Cause

The root cause of this vulnerability is insufficient input validation and lack of bounds checking when processing the page argument in the fromP2pListFilter function. The firmware does not verify that the input data fits within the allocated buffer before copying it to the stack, allowing attackers to overflow the buffer with excessive data.

Attack Vector

The attack is executed by sending a malicious HTTP request to the /goform/P2pListFilter endpoint with a crafted page parameter containing data that exceeds the expected buffer size. Since the attack requires adjacent network access, the attacker must first gain access to the local network where the Tenda CX12L device is deployed.

The vulnerability mechanism involves the router's web management interface accepting user input for the P2P list filtering functionality. When the page parameter is processed without proper length validation, the stack-based buffer overflow occurs. Technical details and proof-of-concept information can be found in the GitHub Issue Discussion and VulDB Vulnerability #355510.

Detection Methods for CVE-2026-5683

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/P2pListFilter with abnormally long page parameter values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Unusual network traffic patterns originating from the router device
• Unexpected changes to router configuration or firmware

Detection Strategies

• Monitor HTTP traffic to the router's management interface for requests containing oversized parameters
• Implement network intrusion detection rules to identify buffer overflow exploitation patterns targeting Tenda devices
• Review router access logs for repeated requests to the /goform/P2pListFilter endpoint
• Deploy network segmentation to limit exposure of router management interfaces

Monitoring Recommendations

• Enable logging on network devices to capture management interface access attempts
• Configure alerts for router availability issues that may indicate exploitation attempts
• Implement continuous monitoring of router configuration integrity
• Use network behavior analysis tools to detect anomalous traffic patterns from IoT and network devices

How to Mitigate CVE-2026-5683

Immediate Actions Required

• Restrict access to the router's web management interface to trusted administrators only
• Implement network segmentation to isolate the router's management interface from untrusted network segments
• Disable remote management features if not required
• 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 confirmed from Tenda. Organizations should monitor the Tenda Official Website for security advisories and firmware updates addressing this vulnerability. Check the VulDB entry for updated mitigation guidance.

Workarounds

• Implement firewall rules to restrict access to the router's management interface (/goform/ endpoints) to specific trusted IP addresses only
• Consider replacing affected devices with alternative hardware if no patch is released in a timely manner
• Use a separate management VLAN for network device administration
• Disable the web management interface entirely and use console access for configuration if possible

# Example firewall rule to restrict management access (iptables)
# Adjust interface and IP addresses as needed for your environment
iptables -A INPUT -i br-lan -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -i br-lan -p tcp --dport 80 -j DROP