CVE-2026-1420: Tenda AC23 Buffer Overflow Vulnerability

CVE-2026-1420 Overview

A buffer overflow vulnerability has been identified in Tenda AC23 router firmware version 16.03.07.52. The vulnerability exists in the /goform/WifiExtraSet endpoint, where improper handling of the wpapsk_crypto argument allows attackers to trigger a buffer overflow condition. This firmware vulnerability in the Tenda AC23 router can be exploited remotely over the network, potentially allowing attackers to execute arbitrary code or cause denial of service on affected devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to compromise Tenda AC23 routers, potentially gaining full control over the device, intercepting network traffic, or using it as a pivot point for further attacks on the network.

Affected Products

• Tenda AC23 Firmware version 16.03.07.52
• Tenda AC23 Hardware

Discovery Timeline

• 2026-01-26 - CVE-2026-1420 published to NVD
• 2026-01-28 - Last updated in NVD database

Technical Details for CVE-2026-1420

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the web management interface of the Tenda AC23 router, specifically within the WifiExtraSet function accessible via the /goform/WifiExtraSet endpoint.

When processing HTTP requests to this endpoint, the firmware fails to properly validate the length of the wpapsk_crypto parameter before copying it into a fixed-size memory buffer. An attacker can craft a malicious request containing an oversized value for this parameter, causing the buffer to overflow and potentially overwriting adjacent memory regions.

The vulnerability can be exploited remotely over the network, requiring only low-level privileges (authenticated access to the router's web interface). No user interaction is required for successful exploitation, and the attack complexity is considered low.

Root Cause

The root cause of this vulnerability is insufficient bounds checking when processing the wpapsk_crypto argument in the WifiExtraSet handler. The firmware copies user-supplied input into a stack or heap buffer without verifying that the input length does not exceed the allocated buffer size. This classic buffer overflow pattern is common in embedded devices where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack is network-based and targets the router's web management interface. An attacker with network access to the router's administration interface can send a specially crafted HTTP POST request to /goform/WifiExtraSet containing a maliciously long wpapsk_crypto parameter value.

The vulnerability has a proof-of-concept exploit that has been publicly disclosed. Technical details and exploitation methodology can be found in the GitHub PoC Repository. The attack can result in complete compromise of the device's confidentiality, integrity, and availability.

Detection Methods for CVE-2026-1420

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/WifiExtraSet with abnormally large wpapsk_crypto parameter values
• Router crashes, reboots, or unresponsive web management interface following network requests
• Anomalous outbound network connections from the router indicating potential compromise
• Modified router configuration settings not authorized by administrators

Detection Strategies

• Deploy network intrusion detection systems (IDS) with rules to identify HTTP requests to /goform/WifiExtraSet containing oversized parameters
• Monitor router logs for failed authentication attempts followed by exploitation attempts
• Implement web application firewall (WAF) rules to limit parameter sizes for router management endpoints
• Use network traffic analysis to detect unusual patterns targeting Tenda devices on the network

Monitoring Recommendations

• Enable verbose logging on the Tenda AC23 router if available and forward logs to a centralized SIEM
• Monitor for firmware integrity changes using scheduled configuration backups and comparison
• Implement network segmentation to isolate IoT devices and routers from critical network segments
• Regularly audit devices on the network for vulnerable firmware versions

How to Mitigate CVE-2026-1420

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote administration if not required for business operations
• Place the router behind a firewall that filters malicious traffic to management endpoints
• Monitor the Tenda Official Website for firmware updates addressing this vulnerability

Patch Information

As of the last update on 2026-01-28, no official patch has been released by Tenda for this vulnerability. Organizations should monitor Tenda's security advisories and apply firmware updates as soon as they become available. Additional technical details about this vulnerability can be found in VulDB #342836.

Workarounds

• Implement network access control lists (ACLs) to restrict access to the router's management interface to authorized IP addresses only
• Disable remote management features and only allow local administration when physically connected to the network
• Consider replacing vulnerable devices with alternative hardware if patches are not forthcoming and the risk is unacceptable
• Deploy a dedicated firewall or security appliance in front of the router to filter malicious requests targeting known vulnerable endpoints

# Example firewall rule to block access to vulnerable endpoint (iptables)
# Adjust interface and IP ranges according to your network configuration
iptables -A INPUT -p tcp --dport 80 -m string --string "/goform/WifiExtraSet" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "/goform/WifiExtraSet" --algo bm -j DROP

# Restrict management interface access to specific trusted IP
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP