CVE-2025-70252: Tenda AC6 Buffer Overflow Vulnerability

CVE-2025-70252 Overview

A stack overflow vulnerability has been discovered in Tenda AC6V2.0 routers running firmware version V15.03.06.23_multi. The vulnerability exists in the /goform/WifiWpsStart endpoint where user-controllable index and mode parameters are concatenated into a buffer using sprintf without proper size validation. This lack of boundary checking allows attackers to overflow the stack buffer, potentially leading to denial of service conditions or further exploitation.

Critical Impact

Network-accessible stack overflow vulnerability in Tenda router firmware allows remote attackers to trigger denial of service conditions without authentication.

Affected Products

• Tenda AC6V2.0 Firmware V15.03.06.23_multi
• Tenda AC6 Router Series (potentially other versions with similar codebase)

Discovery Timeline

• 2026-03-02 - CVE CVE-2025-70252 published to NVD
• 2026-03-03 - Last updated in NVD database

Technical Details for CVE-2025-70252

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The root issue exists within the /goform/WifiWpsStart handler in the Tenda AC6V2 router firmware. When processing WPS configuration requests, the endpoint accepts index and mode parameters from user input. These parameters are directly concatenated into a stack-allocated buffer named tmp using the sprintf function without any bounds checking.

The absence of size validation before the sprintf operation means that overly long input values can write beyond the allocated buffer boundaries, corrupting adjacent stack memory. This memory corruption can lead to denial of service through application crashes, and in more sophisticated attacks, could potentially allow control flow hijacking.

Root Cause

The vulnerability stems from unsafe use of the sprintf function to combine user-controlled input (index and mode parameters) into a fixed-size stack buffer without verifying that the resulting string will fit within the allocated space. The firmware developers failed to implement input length validation or use safer alternatives such as snprintf with appropriate bounds checking.

Attack Vector

An attacker can exploit this vulnerability remotely over the network by sending specially crafted HTTP POST requests to the /goform/WifiWpsStart endpoint. The attack requires no authentication and can be executed without user interaction. By supplying excessively long values for the index or mode parameters, an attacker can trigger a stack buffer overflow condition.

The exploitation typically involves:

1. Identifying a vulnerable Tenda AC6V2 router on the network
2. Crafting an HTTP request to /goform/WifiWpsStart with oversized index or mode parameters
3. Sending the malicious request to corrupt the stack buffer and crash the service or potentially achieve code execution

Technical details and proof-of-concept information are available in the GitHub security research repository.

Detection Methods for CVE-2025-70252

Indicators of Compromise

• Unexpected router crashes or reboots, particularly when WPS functionality is being accessed
• Abnormal HTTP POST requests to /goform/WifiWpsStart with unusually long parameter values
• Network traffic patterns showing repeated connections to router administration endpoints

Detection Strategies

• Monitor HTTP traffic to router management interfaces for POST requests to /goform/WifiWpsStart with parameters exceeding normal length thresholds
• Implement intrusion detection rules to flag requests containing excessively long index or mode parameter values
• Deploy network monitoring to detect unusual patterns of requests targeting router firmware endpoints

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems for traffic directed at router management interfaces
• Configure alerts for repeated crashes or restarts of Tenda router devices in your environment
• Review access logs for the router administration interface for suspicious activity patterns

How to Mitigate CVE-2025-70252

Immediate Actions Required

• Restrict network access to the router administration interface to trusted management networks only
• Implement firewall rules to block external access to router management ports and web interfaces
• Monitor for firmware updates from Tenda addressing this vulnerability
• Consider network segmentation to isolate vulnerable devices from untrusted networks

Patch Information

At the time of publication, users should consult the Tenda security resource page for official firmware updates and security advisories. Organizations should prioritize applying vendor-provided patches as soon as they become available.

Workarounds

• Disable remote administration features on affected routers if not required for operations
• Implement access control lists (ACLs) to restrict which IP addresses can reach the router's web interface
• Use a firewall or security appliance in front of the router to filter and inspect incoming requests to management endpoints
• Consider replacing vulnerable devices with alternatives if no patch is available and the risk is deemed unacceptable

# Example: Block external access to router management interface using iptables
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP