CVE-2026-5605: Tenda CH22 Buffer Overflow Vulnerability

CVE-2026-5605 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda CH22 firmware version 1.0.0.1. This weakness affects the function formWrlExtraSet located in the file /goform/WrlExtraSet. By manipulating the GO argument, an attacker can trigger a stack-based buffer overflow condition. The vulnerability is remotely exploitable over the network, making it a significant security concern for organizations using affected Tenda devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially achieve code execution or cause denial of service on affected Tenda CH22 routers, compromising network infrastructure security.

Affected Products

• Tenda CH22 firmware version 1.0.0.1

Discovery Timeline

• April 6, 2026 - CVE-2026-5605 published to NVD
• April 7, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5605

Vulnerability Analysis

This vulnerability falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The formWrlExtraSet function in the Tenda CH22 firmware fails to properly validate the length of user-supplied input when processing the GO argument. When an attacker sends a specially crafted request to the /goform/WrlExtraSet endpoint with an oversized GO parameter, the function copies this data into a fixed-size stack buffer without adequate bounds checking. This allows the attacker to overwrite adjacent memory on the stack, including saved return addresses and other critical data structures.

The network-accessible nature of this vulnerability significantly increases its risk profile, as attackers do not require local access or authentication to trigger the buffer overflow. The exploit has been disclosed publicly, meaning technical details are available that could enable malicious actors to develop working attack code.

Root Cause

The root cause of CVE-2026-5605 is improper input validation within the formWrlExtraSet function. The firmware does not enforce proper length restrictions when handling the GO parameter, allowing oversized input to overflow stack-allocated buffers. This is a classic buffer overflow scenario where the developers failed to implement adequate boundary checking before copying user-controlled data into fixed-size memory regions.

Attack Vector

The attack is conducted remotely over the network by sending a malicious HTTP request to the /goform/WrlExtraSet endpoint on the Tenda CH22 device. The attacker crafts a request with an excessively long GO parameter value designed to overflow the stack buffer. Upon successful exploitation, the attacker can potentially overwrite the function's return address, redirecting execution flow to attacker-controlled code or causing the device to crash.

The vulnerability requires low privileges to exploit, with no user interaction needed. Successful exploitation can result in high impacts to confidentiality, integrity, and availability of the affected system. For detailed technical information, refer to the GitHub vulnerability disclosure and VulDB entry #355397.

Detection Methods for CVE-2026-5605

Indicators of Compromise

• Unusual HTTP POST requests to /goform/WrlExtraSet containing abnormally long parameter values
• Device crashes, reboots, or unresponsive behavior following web management interface access
• Network traffic anomalies targeting the Tenda CH22 management interface on common web ports

Detection Strategies

• Implement network-based intrusion detection rules to identify HTTP requests to /goform/WrlExtraSet with oversized GO parameters
• Monitor device logs for unexpected restarts or memory corruption errors that may indicate exploitation attempts
• Deploy web application firewall rules to block requests with parameter lengths exceeding expected bounds

Monitoring Recommendations

• Enable logging on network perimeter devices to capture HTTP traffic destined for Tenda router management interfaces
• Establish baseline behavior for the CH22 device and alert on deviations such as unusual resource consumption or connectivity issues
• Implement network segmentation to isolate IoT and networking devices from untrusted network segments

How to Mitigate CVE-2026-5605

Immediate Actions Required

• Restrict access to the Tenda CH22 web management interface to trusted internal networks only
• Implement firewall rules to block external access to the device's administrative ports
• Consider temporarily disabling the web management interface if remote administration is not required
• Monitor for firmware updates from Tenda that address this vulnerability

Patch Information

At the time of publication, no official patch has been confirmed from Tenda for this vulnerability. Organizations should monitor the Tenda official website for security advisories and firmware updates. Until a patch is available, implementing network-level mitigations is critical to reduce exposure.

Workarounds

• Disable remote management access to the Tenda CH22 device entirely if not operationally required
• Place the device behind a VPN or network access control system that requires authentication before reaching the management interface
• Implement network segmentation to prevent untrusted hosts from reaching the device's management ports
• Consider replacing vulnerable devices with alternative networking equipment that has active security support

# Example firewall rule to restrict access to router management interface
# Block external access to common web management ports for Tenda devices
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP