CVE-2026-5156: Tenda CH22 Buffer Overflow Vulnerability

CVE-2026-5156 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda CH22 firmware version 1.0.0.1. This vulnerability impacts the formQuickIndex function within the /goform/QuickIndex endpoint of the Parameter Handler component. An attacker can exploit this flaw by manipulating the mit_linktype argument, causing a stack-based buffer overflow condition. The vulnerability is remotely exploitable over the network, and a proof-of-concept exploit has been publicly disclosed.

Critical Impact

This stack-based buffer overflow vulnerability enables remote attackers to potentially achieve arbitrary code execution on affected Tenda CH22 devices, compromising network infrastructure integrity and confidentiality.

Affected Products

• Tenda CH22 Firmware version 1.0.0.1
• Tenda CH22 Hardware

Discovery Timeline

• 2026-03-31 - CVE-2026-5156 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-5156

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-787 (Out-of-Bounds Write). The flaw exists in the formQuickIndex function, which handles requests to the /goform/QuickIndex endpoint. When processing the mit_linktype parameter, the function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer.

The network-accessible nature of this vulnerability makes it particularly concerning for enterprise and consumer deployments where the device's web interface may be exposed. The vulnerability requires only low privileges to exploit and requires no user interaction, making it an attractive target for automated attack tools.

Root Cause

The root cause of this vulnerability is insufficient input validation in the formQuickIndex function. When the mit_linktype parameter is received from an HTTP request, the application copies the parameter value directly to a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow pattern allows attackers to overwrite adjacent stack memory, including return addresses and saved registers.

Attack Vector

The attack vector is network-based, targeting the web management interface of the Tenda CH22 device. An attacker can craft a malicious HTTP request to the /goform/QuickIndex endpoint with an oversized mit_linktype parameter value. When the vulnerable function processes this request, the excessive input overwrites critical stack data structures.

A successful exploitation could allow the attacker to:

• Execute arbitrary code with the privileges of the web server process
• Crash the device, causing a denial of service
• Pivot to attack other devices on the internal network

Technical details and proof-of-concept information are available in the GitHub PoC Repository.

Detection Methods for CVE-2026-5156

Indicators of Compromise

• Unusual or malformed HTTP POST requests to /goform/QuickIndex containing abnormally long mit_linktype parameter values
• Device crashes or unexpected reboots following web interface access attempts
• Suspicious network traffic patterns targeting the device's management interface from external sources
• Evidence of unauthorized configuration changes or new user accounts on the device

Detection Strategies

• Deploy network intrusion detection systems (IDS) with rules to detect oversized HTTP parameters targeting Tenda device endpoints
• Monitor web server logs for requests to /goform/QuickIndex with unusually large parameter values
• Implement deep packet inspection to identify potential buffer overflow exploitation attempts against IoT devices
• Use network segmentation to isolate management interfaces and enable focused monitoring

Monitoring Recommendations

• Enable verbose logging on network boundary devices to capture traffic destined for IoT management interfaces
• Set up alerts for device availability to detect denial-of-service conditions resulting from exploitation attempts
• Monitor for outbound connections from the affected device to unexpected destinations, which may indicate successful compromise
• Regularly audit device configurations to detect unauthorized changes

How to Mitigate CVE-2026-5156

Immediate Actions Required

• Restrict network access to the Tenda CH22 web management interface to trusted IP addresses only
• Place affected devices behind a firewall and disable direct internet exposure of management interfaces
• Implement network segmentation to isolate IoT devices from critical network assets
• Monitor for exploitation attempts using network security tools

Patch Information

At the time of publication, no official patch from Tenda has been referenced in the available vulnerability data. Organizations should monitor the Tenda Official Website for firmware updates addressing this vulnerability. Additionally, check VulDB #354188 for updated remediation information.

Workarounds

• Disable remote management access to the device if not required for operations
• Configure firewall rules to block external access to the device's web interface (typically port 80/443)
• Use a VPN or jump host for administrative access to reduce attack surface exposure
• Consider replacing affected devices with alternatives that have better security update support if no patch becomes available

# Example firewall configuration to restrict management access
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP