CVE-2026-2181: Tenda RX3 Buffer Overflow Vulnerability

CVE-2026-2181 Overview

A stack-based buffer overflow vulnerability has been discovered in Tenda RX3 wireless router firmware version 16.03.13.11. The vulnerability exists within the /goform/openSchedWifi endpoint, where improper handling of the schedStartTime and schedEndTime parameters allows remote attackers to trigger a buffer overflow condition. This firmware vulnerability in the Tenda RX3 router can be exploited remotely by authenticated attackers, potentially leading to device compromise, arbitrary code execution, or denial of service conditions affecting network infrastructure.

Critical Impact

Remote attackers with low-level privileges can exploit this stack-based buffer overflow to potentially execute arbitrary code or crash the device, compromising network security and availability.

Affected Products

• Tenda RX3 Firmware version 16.03.13.11
• Tenda RX3 Hardware devices running vulnerable firmware

Discovery Timeline

• 2026-02-08 - CVE-2026-2181 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-2181

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the web management interface of the Tenda RX3 router, specifically in the handler function for the /goform/openSchedWifi endpoint. When processing user-supplied input through the schedStartTime and schedEndTime parameters, the firmware fails to properly validate the length of these inputs before copying them to fixed-size stack buffers.

The vulnerability is network-accessible, requiring only low-privilege authentication to exploit. No user interaction is required for successful exploitation, making this a significant security concern for deployed Tenda RX3 devices.

Root Cause

The root cause is improper bounds checking in the firmware's web form handler. When the schedStartTime or schedEndTime parameters are processed, the firmware copies user-supplied data into stack-allocated buffers without verifying that the input length does not exceed the buffer capacity. This classic stack-based buffer overflow pattern allows attackers to overwrite adjacent stack memory, potentially including return addresses and saved registers.

Attack Vector

The attack can be initiated remotely over the network by sending a crafted HTTP POST request to the /goform/openSchedWifi endpoint. An attacker with valid credentials (low privilege required) can manipulate the schedStartTime or schedEndTime parameters with oversized payloads to trigger the buffer overflow condition.

The exploitation involves sending malformed scheduling parameters that exceed expected buffer sizes. When the vulnerable firmware processes these parameters, the overflow corrupts stack memory, which can lead to code execution or denial of service. The exploit methodology has been publicly disclosed and may be used in attacks targeting unpatched Tenda RX3 devices.

Technical details and proof-of-concept information can be found in the GitHub Issue Discussion and the VulDB entry #344884.

Detection Methods for CVE-2026-2181

Indicators of Compromise

• Unusual or malformed HTTP POST requests to /goform/openSchedWifi containing excessively long schedStartTime or schedEndTime parameter values
• Router crashes or unexpected reboots coinciding with web management interface access
• Anomalous network traffic patterns originating from the router after potential exploitation
• Web server logs showing repeated POST requests to scheduling endpoints with oversized payloads

Detection Strategies

• Deploy network intrusion detection systems (IDS) with rules to detect oversized parameters in POST requests to Tenda device management endpoints
• Monitor HTTP traffic for requests targeting /goform/openSchedWifi with parameter values exceeding typical time format lengths
• Implement web application firewall (WAF) rules to block requests with abnormally long scheduling parameters
• Review router access logs for suspicious authentication patterns followed by requests to vulnerable endpoints

Monitoring Recommendations

• Enable comprehensive logging on network firewalls and routers to capture traffic destined for IoT device management interfaces
• Set up alerts for router instability indicators such as unexpected reboots or service interruptions
• Monitor for firmware version information to identify devices running vulnerable version 16.03.13.11
• Implement network segmentation monitoring to detect lateral movement following potential router compromise

How to Mitigate CVE-2026-2181

Immediate Actions Required

• Restrict network access to the Tenda RX3 web management interface to trusted administrative IP addresses only
• Disable remote management features if not required for operations
• Place affected devices behind a properly configured firewall that filters inbound traffic to management ports
• Monitor the Tenda Official Website for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor vendor communications and apply firmware updates as soon as they become available. Additional technical information and tracking can be found at VulDB CTI ID #344884.

Workarounds

• Implement network access control lists (ACLs) to restrict access to the router's web management interface from untrusted networks
• Use a VPN for remote administration rather than exposing the management interface directly to the network
• Change default credentials and implement strong authentication for router management access
• Consider network isolation of affected devices until a patch is available

# Example firewall rule to restrict access to router management interface
# Adjust IP addresses and port numbers according to your environment
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP