CVE-2026-24103: Tenda AC15 Buffer Overflow Vulnerability

CVE-2026-24103 Overview

A buffer overflow vulnerability was discovered in the goform/formSetMacFilterCfg endpoint of the Tenda AC15V1.0 router running firmware version V15.03.05.18_multi. This vulnerability allows remote attackers to exploit memory corruption issues in the router's web management interface, potentially leading to complete device compromise without requiring authentication.

Critical Impact

This network-accessible buffer overflow vulnerability enables unauthenticated remote attackers to potentially execute arbitrary code on affected Tenda AC15 routers, compromising device integrity, confidentiality, and availability.

Affected Products

• Tenda AC15 Hardware Version 1.0
• Tenda AC15 Firmware Version 15.03.05.18_multi
• Tenda AC15 Firmware (all builds of this version)

Discovery Timeline

• 2026-03-03 - CVE-2026-24103 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-24103

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The flaw exists in the formSetMacFilterCfg function within the router's web management interface, which handles MAC address filtering configuration requests.

When processing HTTP requests to the goform/formSetMacFilterCfg endpoint, the firmware fails to properly validate the length of user-supplied input before copying it into a fixed-size memory buffer. This allows an attacker to supply oversized input that overwrites adjacent memory regions, potentially corrupting control flow data such as return addresses or function pointers.

The vulnerability is particularly severe because it can be exploited remotely over the network without any authentication requirements. An attacker with network access to the router's management interface can craft malicious HTTP requests to trigger the buffer overflow condition.

Root Cause

The root cause of this vulnerability is improper input validation in the formSetMacFilterCfg function. The firmware code performs a buffer copy operation using the user-supplied data without first verifying that the input length does not exceed the destination buffer's capacity. This is a classic example of unsafe memory handling in embedded system firmware, where resource constraints often lead developers to use fixed-size buffers without implementing proper bounds checking.

Attack Vector

The attack vector is network-based, requiring the attacker to have access to the router's web management interface. The exploitation flow involves:

1. The attacker identifies a vulnerable Tenda AC15 router accessible over the network
2. A crafted HTTP POST request is sent to the goform/formSetMacFilterCfg endpoint
3. The malicious payload contains oversized input data designed to overflow the target buffer
4. The buffer overflow corrupts adjacent memory, potentially overwriting critical control data
5. Successful exploitation can result in denial of service or arbitrary code execution with router privileges

The vulnerability in goform/formSetMacFilterCfg accepts input parameters related to MAC address filtering configuration. When these parameters exceed expected buffer sizes, the overflow condition occurs in the router's memory space. Due to the nature of embedded systems, successful exploitation could grant the attacker full control over the networking device.

For technical details and proof-of-concept information, refer to the GitHub CVE Reporting Repository.

Detection Methods for CVE-2026-24103

Indicators of Compromise

• Unusual or unexpected HTTP POST requests to goform/formSetMacFilterCfg with abnormally large payloads
• Router instability, unexpected reboots, or unresponsive web management interface
• Anomalous network traffic patterns originating from or directed at the router's management port
• Unauthorized changes to router configuration, particularly MAC filtering settings

Detection Strategies

• Monitor network traffic for HTTP requests to goform/formSetMacFilterCfg containing unusually long parameter values
• Implement intrusion detection rules to flag oversized POST requests to Tenda router management endpoints
• Deploy network segmentation to isolate router management interfaces from untrusted network segments
• Utilize SentinelOne Singularity for network visibility to detect exploitation attempts targeting IoT devices

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems for traffic destined to router management interfaces
• Regularly review router access logs for suspicious activity patterns or failed authentication attempts
• Implement network monitoring to detect unexpected outbound connections from router IP addresses
• Consider deploying dedicated IoT security monitoring solutions for vulnerable embedded devices

How to Mitigate CVE-2026-24103

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management features if not required for operational purposes
• Place the router behind a properly configured firewall that filters management traffic
• Monitor for firmware updates from Tenda and apply patches as soon as they become available

Patch Information

As of the last NVD update on 2026-03-05, no official patch information has been published by Tenda for this vulnerability. Users should monitor the Tenda Product Support Page for firmware updates addressing this security issue.

Organizations should check their firmware version against the affected 15.03.05.18_multi build and prioritize applying any security updates when released by the vendor.

Workarounds

• Configure access control lists (ACLs) on upstream network devices to restrict access to the router's management port (typically TCP port 80 or 443)
• Disable the web management interface entirely if alternative management methods are available
• Implement network segmentation to isolate the vulnerable router from untrusted network segments
• Consider replacing the affected device with an alternative router if patches are not released in a timely manner

# Example: Firewall rule to restrict management access (adjust for your environment)
# Block external access to router management interface
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP
# Allow management access only from trusted admin workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT