CVE-2025-13400: Tenda CH22 Buffer Overflow Vulnerability

CVE-2025-13400 Overview

A buffer overflow vulnerability has been identified in the Tenda CH22 wireless access point running firmware version 1.0.0.1. The vulnerability exists within the formWrlExtraGet function located in the /goform/WrlExtraGet endpoint. An attacker can exploit this vulnerability by manipulating the chkHz argument, triggering a classic buffer overflow condition (CWE-120) that leads to memory corruption (CWE-119). Remote exploitation is possible, and public exploit code is available, increasing the risk of active exploitation.

Critical Impact

This buffer overflow vulnerability enables remote attackers to potentially execute arbitrary code or cause denial of service on affected Tenda CH22 devices. The public availability of exploit code significantly increases exploitation risk.

Affected Products

• Tenda CH22 Firmware version 1.0.0.1
• Tenda CH22 hardware device

Discovery Timeline

• 2025-11-19 - CVE-2025-13400 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2025-13400

Vulnerability Analysis

This vulnerability stems from improper bounds checking in the formWrlExtraGet function when processing the chkHz parameter. The affected function handles HTTP requests to the /goform/WrlExtraGet endpoint without properly validating the length of user-supplied input. When an attacker provides an oversized value for the chkHz argument, the function copies this data into a fixed-size buffer without adequate boundary checks, resulting in a classic buffer overflow condition.

The vulnerability is remotely exploitable over the network, requiring low privilege access to trigger. No user interaction is required for successful exploitation, making this a particularly dangerous attack surface for network-accessible devices.

Root Cause

The root cause is a classic buffer overflow vulnerability (CWE-120) combined with improper restriction of operations within memory buffer bounds (CWE-119). The formWrlExtraGet function fails to properly validate the size of the chkHz parameter before copying it into a stack or heap buffer. This allows attackers to write beyond the allocated buffer boundaries, potentially overwriting adjacent memory structures, return addresses, or function pointers.

Attack Vector

The attack is conducted over the network by sending a specially crafted HTTP request to the /goform/WrlExtraGet endpoint on an affected Tenda CH22 device. The attacker manipulates the chkHz parameter with a malicious payload designed to overflow the buffer and corrupt memory. Successful exploitation could allow an attacker to:

1. Execute arbitrary code on the device with elevated privileges
2. Cause a denial of service condition by crashing the web server or device
3. Potentially gain persistent access to the device

The vulnerability is exploited by sending an HTTP POST or GET request to the vulnerable endpoint with an oversized chkHz parameter value. The request is processed by the formWrlExtraGet function, which copies the parameter value without proper bounds checking. For detailed technical information, see the GitHub Issue Report documenting this vulnerability.

Detection Methods for CVE-2025-13400

Indicators of Compromise

• Unusual HTTP traffic patterns to /goform/WrlExtraGet endpoint containing abnormally large chkHz parameter values
• Unexpected device reboots or service crashes on Tenda CH22 devices
• Suspicious outbound connections from the device following exploitation attempts
• Web server error logs showing malformed requests to the vulnerable endpoint

Detection Strategies

• Monitor network traffic for HTTP requests to Tenda CH22 devices containing oversized parameters in /goform/WrlExtraGet requests
• Implement intrusion detection signatures that alert on buffer overflow patterns targeting embedded device web interfaces
• Deploy network segmentation to isolate IoT and network devices from untrusted networks
• Use SentinelOne Singularity to monitor for anomalous behavior from network infrastructure devices

Monitoring Recommendations

• Enable logging on network firewalls to capture all traffic to Tenda CH22 management interfaces
• Set up alerts for multiple failed requests or unusual request patterns to device management endpoints
• Periodically audit device firmware versions to ensure vulnerable devices are identified
• Monitor for publicly released exploit code targeting this vulnerability via threat intelligence feeds

How to Mitigate CVE-2025-13400

Immediate Actions Required

• Restrict network access to the Tenda CH22 management interface to trusted IP addresses only
• Place affected devices behind a firewall and block external access to port 80/443
• Monitor device behavior for signs of compromise or unusual activity
• Contact Tenda support for firmware update availability
• Consider replacing vulnerable devices if no patch is available

Patch Information

No vendor security patch information is currently available in the CVE data. Organizations should monitor the Tenda Official Website for firmware updates addressing this vulnerability. Additionally, track VulDB #332926 for updated remediation guidance.

Workarounds

• Implement network-level access controls to restrict management interface access to trusted administrators only
• Deploy a web application firewall (WAF) in front of the device to filter malicious requests
• Disable remote management features if not required for operations
• Segment the network to isolate vulnerable devices from critical infrastructure
• Consider using a VPN for remote administration instead of exposing the management interface

Network administrators should implement firewall rules to restrict access to the Tenda CH22 management interface. Configure access control lists to permit connections only from trusted management networks and block all external access to the /goform/ endpoints.