CVE-2026-5604: Tenda CH22 Buffer Overflow Vulnerability

CVE-2026-5604 Overview

A stack-based buffer overflow vulnerability has been discovered in Tenda CH22 firmware version 1.0.0.1. The vulnerability exists in the formCertLocalPrecreate function within the /goform/CertLocalPrecreate endpoint of the Parameter Handler component. By manipulating the standard argument, an attacker can trigger a buffer overflow condition that may lead to remote code execution or denial of service. The exploit has been publicly disclosed and may be actively used in attacks.

Critical Impact

This network-accessible stack-based buffer overflow allows remote authenticated attackers to potentially execute arbitrary code, compromise device integrity, or cause system instability on affected Tenda CH22 routers.

Affected Products

• Tenda CH22 firmware version 1.0.0.1

Discovery Timeline

• 2026-04-05 - CVE-2026-5604 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-5604

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 formCertLocalPrecreate function, which handles certificate-related operations on the Tenda CH22 router. When processing the standard parameter sent to the /goform/CertLocalPrecreate endpoint, the function fails to properly validate the length of user-supplied input before copying it into a fixed-size stack buffer.

The network-accessible nature of this vulnerability means that any authenticated attacker with network access to the device's web management interface can potentially exploit this flaw without any user interaction. Successful exploitation could allow an attacker to overwrite return addresses on the stack, potentially leading to arbitrary code execution with the privileges of the web server process.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the formCertLocalPrecreate function when handling the standard parameter. The function allocates a fixed-size buffer on the stack but fails to verify that the incoming data fits within the allocated space. This classic buffer overflow pattern allows attackers to write beyond the intended buffer boundaries, corrupting adjacent stack memory including saved return addresses and function pointers.

Attack Vector

The attack vector is network-based, targeting the web management interface of the Tenda CH22 router. An attacker can craft a malicious HTTP request to the /goform/CertLocalPrecreate endpoint containing an oversized standard parameter value. When the vulnerable function processes this request, the excessively long input overflows the stack buffer. With careful crafting of the payload, an attacker could potentially redirect execution flow to arbitrary code, enabling device takeover. Technical details of the vulnerability have been published to the GitHub vulnerability repository and tracked in VulDB #355396.

Detection Methods for CVE-2026-5604

Indicators of Compromise

• Unusual HTTP POST requests to /goform/CertLocalPrecreate containing abnormally long standard parameter values
• Unexpected router reboots or crashes following web management interface access
• Signs of unauthorized configuration changes or firmware modifications on Tenda CH22 devices
• Suspicious network traffic originating from the router to unknown external destinations

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests targeting /goform/CertLocalPrecreate with oversized parameter payloads
• Monitor web server logs on Tenda CH22 devices for requests with anomalous parameter lengths exceeding expected bounds
• Deploy endpoint detection solutions capable of identifying buffer overflow exploitation patterns
• Configure alerts for repeated authentication attempts followed by requests to vulnerable endpoints

Monitoring Recommendations

• Enable comprehensive logging on the router's web management interface if available
• Implement network traffic analysis to detect payload patterns consistent with buffer overflow attempts
• Monitor for firmware integrity changes that could indicate post-exploitation persistence
• Review access logs for requests from unexpected IP addresses targeting the vulnerable endpoint

How to Mitigate CVE-2026-5604

Immediate Actions Required

• Restrict network access to the Tenda CH22 web management interface to trusted administrative hosts only
• Place affected devices behind a firewall and disable remote management access from untrusted networks
• Monitor for firmware updates from Tenda that address this vulnerability
• Consider replacing affected devices with models that have received security patches if no update is available

Patch Information

At the time of publication, no vendor patch has been confirmed for this vulnerability. Administrators should monitor the Tenda Official Website for security updates addressing CVE-2026-5604. Given the public disclosure of exploitation details, applying patches immediately upon availability is strongly recommended.

Workarounds

• Disable the web management interface entirely if remote administration is not required
• Implement strict access control lists (ACLs) limiting management interface access to specific trusted IP addresses
• Deploy a web application firewall (WAF) to filter requests with oversized parameters targeting the vulnerable endpoint
• Segment the network to isolate affected Tenda CH22 devices from untrusted network segments

# Example: Restrict management interface access via firewall rules
# Block external access to the router management port (typically 80/443)
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