CVE-2025-12595: Tenda AC23 Buffer Overflow Vulnerability

CVE-2025-12595 Overview

A buffer overflow vulnerability has been identified in Tenda AC23 router firmware version 16.03.07.52. This security flaw impacts the formSetVirtualSer function within the /goform/SetVirtualServerCfg file. By manipulating the list argument, an attacker can trigger a buffer overflow condition. This vulnerability can be exploited remotely over the network and poses a significant risk to affected devices. The exploit details have been made publicly available, increasing the potential for malicious exploitation.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow to potentially execute arbitrary code, crash the device, or gain unauthorized control over the affected Tenda AC23 router.

Affected Products

• Tenda AC23 Firmware version 16.03.07.52
• Tenda AC23 Hardware version 1.0

Discovery Timeline

• 2025-11-02 - CVE-2025-12595 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2025-12595

Vulnerability Analysis

This vulnerability exists in the formSetVirtualSer function, which is responsible for handling virtual server configuration requests on the Tenda AC23 router. The function processes user-supplied input through the list parameter without proper bounds checking, leading to a classic buffer overflow condition (CWE-120: Buffer Copy without Checking Size of Input).

The underlying issue is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), indicating that the firmware fails to properly constrain memory operations when processing the malicious input. This allows attackers to write data beyond the intended buffer boundaries, potentially corrupting adjacent memory regions.

The network-accessible nature of this vulnerability through the /goform/SetVirtualServerCfg endpoint makes it particularly dangerous, as it can be exploited remotely without requiring physical access to the device. An attacker with low-level privileges can craft malicious requests to the web management interface to trigger the overflow condition.

Root Cause

The root cause of this vulnerability is insufficient input validation in the formSetVirtualSer function. The function accepts the list argument from HTTP requests processed through the router's web interface without adequately verifying the size of the input data before copying it into a fixed-size memory buffer. This lack of bounds checking is a fundamental programming error that leads to the buffer overflow condition.

Attack Vector

The attack vector for CVE-2025-12595 is network-based, requiring the attacker to send specially crafted HTTP requests to the vulnerable endpoint /goform/SetVirtualServerCfg. The attack requires low-level privileges and no user interaction.

An attacker would typically:

1. Identify a vulnerable Tenda AC23 router on the network
2. Craft a malicious HTTP POST request to /goform/SetVirtualServerCfg
3. Include an oversized or specially crafted value for the list parameter
4. The formSetVirtualSer function processes this input and overflows the buffer
5. Depending on the payload, this could lead to denial of service, code execution, or device compromise

Technical details and proof-of-concept information are available through the GitHub Issue Discussion and VulDB entry #330890.

Detection Methods for CVE-2025-12595

Indicators of Compromise

• Unusual HTTP POST requests to /goform/SetVirtualServerCfg with abnormally large list parameter values
• Unexpected router crashes or reboots that may indicate exploitation attempts
• Anomalous network traffic patterns targeting router management interfaces
• Unauthorized configuration changes on the Tenda AC23 router

Detection Strategies

• Deploy network intrusion detection systems (IDS) rules to monitor for oversized POST requests to /goform/SetVirtualServerCfg
• Implement web application firewall (WAF) rules to filter requests with excessively long parameter values
• Enable logging on the router management interface and monitor for suspicious access patterns
• Use SentinelOne Singularity to detect network-based exploitation attempts targeting IoT devices

Monitoring Recommendations

• Continuously monitor network traffic to and from Tenda AC23 routers for anomalous patterns
• Implement alerting for repeated requests to virtual server configuration endpoints
• Regularly review router logs for authentication failures or unusual administrative access
• Consider network segmentation to isolate IoT devices from critical infrastructure

How to Mitigate CVE-2025-12595

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management capabilities if not strictly required
• Place the Tenda AC23 router behind a firewall with rules blocking external access to management ports
• Implement network segmentation to limit potential lateral movement if the device is compromised
• Monitor for firmware updates from Tenda that address this vulnerability

Patch Information

At the time of this writing, no official patch information has been published by Tenda. Users are advised to monitor the Tenda Official Website for security updates and firmware releases that address CVE-2025-12595. Additional vulnerability details can be found in the VulDB entry.

Workarounds

• Disable remote administration access to the router's web interface
• Implement IP-based access control lists (ACLs) to restrict management interface access
• Deploy a dedicated firewall in front of the router to filter malicious requests
• Consider replacing the vulnerable device with a supported alternative if no patch becomes available
• Use VPN-only access for remote administration needs

# Recommended network segmentation example using iptables
# Block external access to router management interface
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP