CVE-2025-12225: Tenda AC6 Buffer Overflow Vulnerability

CVE-2025-12225 Overview

CVE-2025-12225 is a stack-based buffer overflow vulnerability in the Tenda AC6 router running firmware version 15.03.06.50. The flaw resides in the HTTP Request Handler component, specifically in the processing of the /goform/WifiGuestSet endpoint. Manipulation of the shareSpeed argument triggers the overflow on the device stack. The vulnerability is remotely exploitable across the network and a public exploit description has been disclosed. The issue is tracked under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and impacts confidentiality, integrity, and availability of the affected device.

Critical Impact
Remote attackers with low privileges can corrupt the stack of the httpd process on Tenda AC6 routers, potentially leading to arbitrary code execution or denial of service.

Affected Products

Tenda AC6 router (hardware revision 2.0)
Tenda AC6 firmware version 15.03.06.50
Devices exposing the web management interface (/goform/WifiGuestSet)

Discovery Timeline

2025-10-27 - CVE-2025-12225 published to NVD
2025-10-28 - Last updated in NVD database

Technical Details for CVE-2025-12225

Vulnerability Analysis

The vulnerability resides in the HTTP request handler that services the /goform/WifiGuestSet form action on the Tenda AC6 web interface. This endpoint configures the guest Wi-Fi network and accepts several POST parameters, including shareSpeed. The handler copies the attacker-supplied shareSpeed value into a fixed-size stack buffer without validating its length. An overly long value overflows the buffer and overwrites adjacent stack memory, including saved registers and the return address on the MIPS-based device. The EPSS score is 0.848% with a percentile of 53.136, reflecting moderate exploitation likelihood. Successful exploitation can crash the httpd daemon or hijack control flow to execute attacker-controlled instructions on the router.

Root Cause

The root cause is missing bounds checking when the HTTP handler processes the shareSpeed parameter. The function uses an unsafe string copy operation to move user-controlled data into a stack-allocated buffer. Because no length validation precedes the copy, attacker input larger than the buffer corrupts the call stack.

Attack Vector

An authenticated attacker with low-privilege access to the router's web interface sends a crafted HTTP POST request to /goform/WifiGuestSet containing an oversized shareSpeed value. The request reaches the handler, triggers the overflow, and may overwrite the saved return address. On embedded MIPS targets without modern stack protections, this can be leveraged for remote code execution against the router. Technical details and a proof of concept are documented in the GitHub PoC Repository and indexed in VulDB Item #329895.

Detection Methods for CVE-2025-12225

Indicators of Compromise

HTTP POST requests to /goform/WifiGuestSet containing an unusually long shareSpeed parameter value.
Unexpected restarts, crashes, or watchdog reboots of the httpd service on Tenda AC6 devices.
Outbound connections from the router to unknown hosts following web management traffic spikes.
Web management session activity from low-privilege accounts immediately preceding device instability.

Detection Strategies

Inspect HTTP request bodies destined for the router's management interface and flag shareSpeed values exceeding expected length limits.
Hunt for repeated requests to /goform/WifiGuestSet from the same source within short time windows.
Correlate router syslog or SNMP traps showing httpd crashes with prior administrative HTTP requests.

Monitoring Recommendations

Enable verbose logging on perimeter devices to capture HTTP requests to embedded device management URLs.
Forward router logs to a centralized logging platform and alert on process restarts.
Restrict and audit the source networks permitted to reach the router's administrative interface.

How to Mitigate CVE-2025-12225

Immediate Actions Required

Disable remote (WAN-side) administration on the Tenda AC6 and limit web management access to a trusted management VLAN.
Change all default and low-privilege router credentials and enforce strong passwords on the web interface.
Disable the guest Wi-Fi configuration feature if it is not in active use to reduce exposure of the vulnerable endpoint.
Segment the router's management plane from user and IoT networks.

Patch Information

No vendor patch has been published in the referenced advisories at the time of disclosure. Monitor the Tenda Official Website for firmware updates addressing the WifiGuestSet handler. If the device is end-of-life or no firmware update is forthcoming, plan replacement with a supported model.

Workarounds

Block external access to TCP ports used by the router's HTTP management interface at the upstream firewall.
Place the affected device behind a network ACL that permits administrative HTTP traffic only from a dedicated admin host.
Deploy an intrusion prevention signature that drops POST requests to /goform/WifiGuestSet containing shareSpeed values longer than the legitimate field length.

bash

# Example iptables rule restricting router web admin to a single admin host
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.10 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP