CVE-2026-2185: Tenda RX3 Buffer Overflow Vulnerability

CVE-2026-2185 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda RX3 firmware version 16.03.13.11. This critical flaw affects the set_device_name function within the /goform/setBlackRule file, which is part of the MAC Filtering Configuration Endpoint. Attackers can exploit this vulnerability by manipulating the devName or mac arguments, potentially leading to remote code execution or denial of service conditions on affected devices.

Critical Impact

This vulnerability allows remote attackers to exploit a stack-based buffer overflow in Tenda RX3 routers, potentially enabling arbitrary code execution with elevated privileges on the device. The exploit has been publicly disclosed, increasing the risk of active exploitation.

Affected Products

• Tenda RX3 Firmware version 16.03.13.11
• Tenda RX3 hardware devices
• Tenda RX3 routers running vulnerable firmware versions

Discovery Timeline

• 2026-02-08 - CVE-2026-2185 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-2185

Vulnerability Analysis

This vulnerability is classified as a stack-based buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the set_device_name function that processes MAC filtering configuration requests through the /goform/setBlackRule endpoint.

When processing the devName and mac parameters, the function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer. An attacker can supply overly long values for these parameters, causing the buffer to overflow and overwrite adjacent memory on the stack, including potentially critical control data such as return addresses.

The vulnerability is exploitable remotely over the network, requiring only low privileges to authenticate to the router's web management interface. No user interaction is required beyond the initial request, making this a particularly dangerous flaw for consumer network devices.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the set_device_name function when handling the devName and mac input parameters. The function allocates a fixed-size buffer on the stack to store these values but does not verify that the incoming data length does not exceed the allocated buffer size before performing memory copy operations. This classic buffer overflow pattern allows attackers to corrupt stack memory and potentially hijack program execution flow.

Attack Vector

The attack vector is network-based, targeting the /goform/setBlackRule endpoint on the Tenda RX3 router's web management interface. An attacker with low-level access to the router (such as basic authentication credentials) can craft malicious HTTP POST requests containing oversized values for the devName or mac parameters.

The exploitation flow involves:

1. Authenticating to the router's web interface with valid credentials
2. Sending a crafted POST request to /goform/setBlackRule
3. Including maliciously long strings in the devName or mac parameters
4. Overflowing the stack buffer to overwrite return addresses
5. Redirecting execution to attacker-controlled code or payload

For technical details and proof-of-concept information, refer to the GitHub Issue Discussion and VulDB Entry #344888.

Detection Methods for CVE-2026-2185

Indicators of Compromise

• Unusual or oversized HTTP POST requests to /goform/setBlackRule endpoint
• Crash logs or unexpected reboots of the Tenda RX3 router
• Abnormal network traffic patterns originating from the router
• Modified firmware or configuration files on the device

Detection Strategies

• Monitor HTTP traffic to the router's web management interface for POST requests to /goform/setBlackRule containing abnormally long devName or mac parameter values
• Implement network intrusion detection rules to flag requests exceeding expected parameter lengths for MAC filtering endpoints
• Deploy endpoint detection solutions to identify buffer overflow exploitation attempts on IoT devices
• Review router access logs for authentication attempts followed by configuration endpoint access

Monitoring Recommendations

• Enable logging on the Tenda RX3 router to capture all management interface access attempts
• Implement network segmentation to isolate IoT devices and monitor traffic crossing segment boundaries
• Deploy network traffic analysis tools to identify anomalous patterns targeting router management ports
• Establish baseline behavior for router management traffic and alert on deviations

How to Mitigate CVE-2026-2185

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not explicitly required
• Implement strong, unique credentials for router administration
• Consider placing the router behind a firewall that filters malicious requests

Patch Information

As of the last update on 2026-02-10, no official patch has been released by Tenda for this vulnerability. Users should monitor the Tenda official website for firmware updates addressing CVE-2026-2185. Given the public disclosure of this exploit, organizations should prioritize applying patches immediately upon availability.

For additional technical information, consult the VulDB CTI Entry for ongoing threat intelligence updates.

Workarounds

• Disable the web management interface entirely if router configuration changes are not frequently needed
• Implement access control lists (ACLs) to restrict management interface access to specific trusted IP addresses
• Deploy a web application firewall (WAF) in front of the router management interface to filter malicious requests
• Consider replacing vulnerable Tenda RX3 devices with alternative hardware until a patch is available

# Example: Restrict management access via firewall rules
# Block external access to router management port (typically port 80/443)
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