CVE-2026-4840: Netcore Power 15AX RCE Vulnerability

CVE-2026-4840 Overview

A critical OS command injection vulnerability has been discovered in Netcore Power 15AX routers running firmware versions up to 3.0.0.6938. The vulnerability exists in the setTools function within the /bin/netis.cgi component, specifically in the Diagnostic Tool Interface. An attacker can manipulate the IpAddr argument to inject arbitrary operating system commands, enabling remote code execution on the affected device.

Critical Impact

Remote attackers with low-privilege access can execute arbitrary OS commands on vulnerable Netcore Power 15AX routers, potentially leading to complete device compromise, network infiltration, and persistent backdoor installation.

Affected Products

• Netcore Power 15AX firmware versions up to 3.0.0.6938
• Devices with the Diagnostic Tool Interface accessible via /bin/netis.cgi

Discovery Timeline

• 2026-03-26 - CVE-2026-4840 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2026-4840

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Command Injection), where user-supplied input is passed directly to a system shell without proper sanitization. The Diagnostic Tool Interface in Netcore Power 15AX routers provides network diagnostic functionality that accepts IP addresses as input parameters. The setTools function in /bin/netis.cgi processes the IpAddr argument without adequate input validation, allowing attackers to break out of the intended command context and inject arbitrary shell commands.

The attack can be executed remotely over the network, requiring only low-privilege authentication to access the diagnostic interface. Once exploited, an attacker gains the ability to execute commands with the privileges of the web server process, which on embedded devices like routers typically runs with elevated or root permissions.

Root Cause

The root cause of this vulnerability is improper input validation and failure to sanitize user-supplied data before passing it to system shell functions. The setTools function directly incorporates the IpAddr parameter into shell commands used for network diagnostics (such as ping or traceroute operations) without escaping shell metacharacters or validating the input format. This allows an attacker to terminate the intended command and append malicious commands using shell metacharacters such as ;, |, &&, or backticks.

Attack Vector

The attack is conducted remotely over the network by sending a crafted HTTP request to the /bin/netis.cgi endpoint. An authenticated attacker with low-privilege access to the router's web interface can navigate to the Diagnostic Tool Interface and submit a malicious payload in the IpAddr field.

For example, instead of providing a legitimate IP address like 192.168.1.1, an attacker could supply a value containing shell metacharacters followed by arbitrary commands. The injected commands would then be executed by the underlying operating system when the diagnostic function processes the input.

A proof-of-concept for this vulnerability has been publicly released and documented in the GitHub CVE PoC Repository. The vendor was contacted about this disclosure but did not respond, leaving users without an official patch.

Detection Methods for CVE-2026-4840

Indicators of Compromise

• Unexpected HTTP requests to /bin/netis.cgi containing shell metacharacters (;, |, &&, `) in the IpAddr parameter
• Anomalous process spawning from the web server process on the router
• Unusual outbound network connections originating from the router to unknown external hosts
• Evidence of reverse shell connections or command-and-control traffic from the device

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests containing command injection patterns targeting /bin/netis.cgi
• Monitor router logs for diagnostic tool usage with malformed or suspicious IP address values
• Deploy network traffic analysis to detect unusual egress traffic from router management interfaces
• Use SentinelOne Singularity to monitor for anomalous process behavior and command execution patterns on network infrastructure

Monitoring Recommendations

• Enable logging on the Netcore Power 15AX router and forward logs to a SIEM for centralized analysis
• Establish baseline network behavior for router management traffic and alert on deviations
• Regularly audit access to the router's web administration interface and diagnostic tools

How to Mitigate CVE-2026-4840

Immediate Actions Required

• Restrict network access to the router's web administration interface to trusted management networks only
• Disable the Diagnostic Tool Interface if it is not required for operational purposes
• Implement network-level access controls (firewall rules, VLANs) to prevent untrusted users from reaching the management interface
• Consider replacing affected devices with alternatives from vendors with active security support

Patch Information

No official patch is currently available from the vendor. According to the vulnerability disclosure, the vendor was contacted early about this security issue but did not respond. Users should monitor for firmware updates and consider alternative mitigation strategies until a patch is released. Additional technical details are available at VulDB #353146.

Workarounds

• Restrict access to the web management interface by configuring firewall rules to allow only trusted IP addresses
• Place the router's management interface on a separate, isolated network segment inaccessible from untrusted networks
• Disable remote management features if not required and manage the device only via local console access
• Deploy a web application firewall (WAF) or reverse proxy in front of the management interface to filter command injection attempts

# Example: iptables rule to restrict management interface access
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP