CVE-2025-12265: Tenda CH22 Buffer Overflow Vulnerability

CVE-2025-12265 Overview

A buffer overflow vulnerability has been identified in Tenda CH22 firmware version 1.0.0.1. The vulnerability exists in the fromVirtualSer function located in the /goform/VirtualSer endpoint. An attacker can exploit this weakness by manipulating the page argument, causing a buffer overflow condition. This vulnerability is remotely exploitable over the network, and exploit information has been made publicly available, increasing the risk of active exploitation attempts.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow vulnerability to potentially execute arbitrary code or cause denial of service on affected Tenda CH22 devices running firmware version 1.0.0.1.

Affected Products

• Tenda CH22 Firmware version 1.0.0.1
• Tenda CH22 Hardware (all versions with affected firmware)

Discovery Timeline

• 2025-10-27 - CVE-2025-12265 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2025-12265

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), a fundamental memory corruption issue. The vulnerable function fromVirtualSer fails to properly validate the length of user-supplied input through the page parameter before copying it into a fixed-size buffer. This lack of bounds checking allows attackers to write data beyond the allocated buffer boundaries, potentially overwriting adjacent memory regions including return addresses, function pointers, or other critical data structures.

The network-accessible nature of the vulnerable endpoint (/goform/VirtualSer) significantly increases the attack surface, as exploitation can be performed remotely without physical access to the device. The low attack complexity and minimal authentication requirements make this vulnerability particularly dangerous in environments where Tenda CH22 devices are exposed to untrusted networks.

Root Cause

The root cause of this vulnerability stems from improper input validation in the fromVirtualSer function. The function accepts user-controlled data through the page argument without adequately verifying that the input length does not exceed the destination buffer's capacity. This is a classic buffer overflow pattern commonly found in embedded device firmware where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack vector is network-based, targeting the /goform/VirtualSer HTTP endpoint on vulnerable Tenda CH22 devices. An authenticated attacker with low-level privileges can craft a malicious HTTP request containing an oversized page parameter value. When the fromVirtualSer function processes this input, the buffer overflow occurs, potentially allowing the attacker to:

1. Corrupt adjacent memory structures
2. Hijack program execution flow by overwriting return addresses
3. Execute arbitrary code with the privileges of the web server process
4. Cause a denial of service condition by crashing the device

The vulnerability requires only low-privilege authentication and no user interaction, making automated exploitation feasible. Technical details and discussion can be found in the GitHub Issue Discussion and VulDB advisory #329936.

Detection Methods for CVE-2025-12265

Indicators of Compromise

• Unusual HTTP POST requests to /goform/VirtualSer with abnormally long page parameter values
• Device crashes or unexpected reboots that may indicate exploitation attempts
• Anomalous network traffic patterns originating from Tenda CH22 devices
• Web server process crashes in device logs

Detection Strategies

• Implement network-based intrusion detection rules to identify malformed requests targeting /goform/VirtualSer with oversized parameters
• Monitor for HTTP requests containing page parameters exceeding expected length boundaries
• Deploy web application firewalls (WAF) to filter malicious payloads targeting the vulnerable endpoint
• Enable verbose logging on Tenda devices to capture exploitation attempts

Monitoring Recommendations

• Continuously monitor network traffic to and from Tenda CH22 devices for anomalous patterns
• Implement alerting for repeated crashes or restarts of affected devices
• Review device access logs for suspicious authentication patterns followed by requests to /goform/VirtualSer
• Consider network segmentation to isolate IoT devices from critical infrastructure

How to Mitigate CVE-2025-12265

Immediate Actions Required

• Restrict network access to the Tenda CH22 management interface to trusted IP addresses only
• Implement firewall rules to block external access to the /goform/VirtualSer endpoint
• Place affected devices behind a properly configured network firewall or VPN
• Disable remote administration if not required for operational purposes
• Monitor the Tenda website for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no vendor patch has been confirmed for this vulnerability. Organizations should monitor official Tenda channels for security updates and apply patches immediately when available. Given the public availability of exploit information, patching should be treated as a high priority.

Workarounds

• Implement network access controls to limit connectivity to affected devices to authorized administrators only
• Deploy a reverse proxy or web application firewall in front of the device to filter malicious requests containing oversized page parameters
• Consider replacing affected devices with alternative products if Tenda does not release a timely patch
• Temporarily disable the VirtualSer functionality if it is not operationally required

# Example firewall rule to restrict access to Tenda CH22 management interface
# Replace 192.168.1.100 with your Tenda CH22 device IP
# Replace 10.0.0.0/24 with your trusted management network

iptables -A INPUT -d 192.168.1.100 -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -d 192.168.1.100 -p tcp --dport 80 -j DROP