CVE-2025-12271: Tenda CH22 Buffer Overflow Vulnerability

CVE-2025-12271 Overview

A buffer overflow vulnerability has been identified in Tenda CH22 firmware version 1.0.0.1. This security flaw affects the fromRouteStatic function within the /goform/RouteStatic file. Improper handling of the page argument allows an attacker to trigger a buffer overflow condition. The vulnerability can be exploited remotely over the network, and technical details regarding the exploit are publicly available.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow to potentially achieve code execution, compromise device integrity, and cause denial of service on affected Tenda CH22 devices.

Affected Products

• Tenda CH22 Firmware version 1.0.0.1
• Tenda CH22 Hardware (all versions)

Discovery Timeline

• 2025-10-27 - CVE-2025-12271 published to NVD
• 2025-10-28 - Last updated in NVD database

Technical Details for CVE-2025-12271

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists in the fromRouteStatic function, which processes HTTP requests sent to the /goform/RouteStatic endpoint on the Tenda CH22 router. When the page argument is manipulated with malicious input, the function fails to properly validate the input length before copying it into a fixed-size buffer, resulting in a classic buffer overflow condition.

The network-accessible nature of this vulnerability significantly increases its risk profile. An authenticated attacker with low privileges can remotely submit crafted requests to the vulnerable endpoint. Successful exploitation could allow an attacker to overwrite adjacent memory regions, potentially leading to arbitrary code execution, device compromise, or denial of service.

Root Cause

The root cause stems from insufficient bounds checking in the fromRouteStatic function when processing the page parameter. The firmware does not validate the size of user-supplied input before copying it into a stack or heap buffer, allowing an attacker to write beyond the allocated memory boundaries. This is a common vulnerability pattern in embedded device firmware where memory-safe programming practices are not consistently applied.

Attack Vector

The attack vector is network-based, requiring the attacker to send specially crafted HTTP POST requests to the /goform/RouteStatic endpoint. The attacker must have low-level authentication to the device's web interface. By manipulating the page parameter with an oversized or malformed value, the attacker can overflow the destination buffer.

The vulnerability mechanism works as follows: When the router processes a request to /goform/RouteStatic, the fromRouteStatic function extracts the page parameter from the request. Due to the lack of input length validation, an attacker-controlled string of excessive length overwrites stack or heap memory beyond the intended buffer boundaries. This can corrupt adjacent variables, return addresses, or function pointers, potentially allowing the attacker to hijack program execution flow.

For detailed technical analysis and proof-of-concept information, refer to the GitHub CVE Issue Discussion and VulDB Details #329943.

Detection Methods for CVE-2025-12271

Indicators of Compromise

• Unusual HTTP POST requests to /goform/RouteStatic with abnormally large page parameter values
• Device crashes, reboots, or unresponsive behavior following web interface interactions
• Unexpected modifications to device configuration or firmware
• Anomalous network traffic patterns originating from the router

Detection Strategies

• Monitor HTTP traffic to Tenda CH22 devices for requests to /goform/RouteStatic containing oversized parameter values
• Implement intrusion detection rules to flag HTTP POST requests with page parameters exceeding normal length thresholds
• Deploy network-based anomaly detection to identify potential exploitation attempts against IoT devices
• Review web server logs on management interfaces for suspicious request patterns

Monitoring Recommendations

• Enable logging on network perimeter devices to capture traffic destined for Tenda router management interfaces
• Configure SIEM alerts for repeated failed authentication attempts or unusual request patterns targeting router endpoints
• Implement network segmentation to isolate IoT devices and monitor cross-segment communication
• Regularly audit device behavior for signs of compromise such as unexpected configuration changes

How to Mitigate CVE-2025-12271

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 remote management if not required
• Monitor vendor channels for firmware updates addressing this vulnerability
• Consider network isolation of affected devices until a patch is available

Patch Information

At the time of this publication, no official patch has been released by Tenda for this vulnerability. Administrators should monitor the Tenda Security Information page for firmware updates. Given the publicly available nature of the exploit, applying patches promptly upon release is critical.

Workarounds

• Disable remote access to the web management interface and only allow local administration
• Implement firewall rules to block external access to port 80/443 on the Tenda CH22 device
• Use VPN or jump host for administrative access rather than exposing the management interface directly
• Consider replacing affected devices with alternatives if vendor support is not forthcoming

# Example firewall rule to restrict access to Tenda CH22 management interface
# Allow only trusted management subnet
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