CVE-2026-4620: NEC Aterm Series RCE Vulnerability

CVE-2026-4620 Overview

CVE-2026-4620 is an OS Command Injection vulnerability affecting NEC Platforms, Ltd. Aterm Series network devices. This vulnerability allows an attacker to execute arbitrary operating system commands via the network, potentially leading to complete device compromise, unauthorized access to network infrastructure, and lateral movement within affected environments.

Critical Impact

Successful exploitation allows attackers to execute arbitrary OS commands on affected Aterm Series devices, potentially compromising network infrastructure and enabling further attacks on connected systems.

Affected Products

• NEC Platforms, Ltd. Aterm Series devices

Discovery Timeline

• 2026-03-27 - CVE CVE-2026-4620 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2026-4620

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The flaw exists within the Aterm Series network devices manufactured by NEC Platforms, Ltd., where user-supplied input is passed to system shell commands without adequate sanitization or validation.

OS Command Injection vulnerabilities occur when an application constructs operating system commands using externally-influenced input without proper neutralization of special elements. In this case, the vulnerability can be exploited over the network, though it requires authenticated access with high privileges and active user interaction, indicating the attack complexity is elevated compared to simpler injection flaws.

The network-accessible nature of this vulnerability is particularly concerning for router and network device deployments, as these devices often serve as critical infrastructure components. Successful exploitation could lead to complete confidentiality, integrity, and availability compromise of the affected device.

Root Cause

The root cause of CVE-2026-4620 lies in insufficient input validation and sanitization within the Aterm Series device firmware. When processing certain network-accessible functionality, the device fails to properly neutralize special characters and command operators (such as ;, |, &, $(), and backticks) that could be interpreted as shell metacharacters.

This allows an attacker who meets the prerequisite conditions to inject malicious commands that are then executed by the underlying operating system with the privileges of the web server or management interface process.

Attack Vector

The attack vector for CVE-2026-4620 is network-based, meaning an attacker can exploit this vulnerability remotely without physical access to the device. However, several conditions must be met for successful exploitation:

1. High Privileges Required - The attacker needs authenticated access with elevated privileges on the target device
2. User Interaction - Active user interaction is required as part of the attack chain
3. Network Access - The attacker must have network connectivity to the vulnerable device's management interface

The exploitation scenario involves an authenticated attacker with administrative or privileged access crafting malicious input containing OS command injection payloads. When this input is processed by vulnerable functionality within the device, the injected commands are executed on the underlying operating system.

Exploitation typically involves injecting shell metacharacters followed by arbitrary commands into vulnerable input fields or parameters accessible through the device's network interface. For detailed technical information about the vulnerability, refer to the NEC Security Information Advisory.

Detection Methods for CVE-2026-4620

Indicators of Compromise

• Unusual outbound network connections from Aterm Series devices to unknown external IP addresses
• Unexpected processes or services running on the affected device
• Suspicious authentication attempts or logins to device management interfaces from unfamiliar sources
• Anomalous command execution patterns or shell activity in device logs

Detection Strategies

• Monitor network traffic to and from Aterm Series devices for suspicious patterns, including unusual DNS queries or connections to known malicious infrastructure
• Implement network intrusion detection rules to identify potential command injection payloads in HTTP/HTTPS traffic destined for device management interfaces
• Deploy SentinelOne Singularity for network visibility and behavioral detection of compromised IoT/network devices
• Review device access logs for unauthorized or anomalous administrative access attempts

Monitoring Recommendations

• Enable comprehensive logging on Aterm Series devices and forward logs to a centralized SIEM solution
• Establish baseline network behavior for Aterm devices and alert on deviations
• Implement periodic integrity checks of device firmware and configuration
• Monitor for changes to device configurations or the creation of new administrative accounts

How to Mitigate CVE-2026-4620

Immediate Actions Required

• Review the NEC Security Information Advisory for affected product versions and available patches
• Restrict network access to device management interfaces using firewall rules or network segmentation
• Limit administrative access to trusted users and implement strong authentication practices
• Disable unnecessary network services on affected devices until patches can be applied

Patch Information

NEC Platforms, Ltd. has published security information regarding this vulnerability. Administrators should consult the official NEC Security Information Advisory for specific patch availability, affected firmware versions, and detailed remediation guidance.

Organizations should prioritize applying vendor-provided firmware updates as they become available. Prior to deploying patches in production environments, testing in a non-production environment is recommended to ensure compatibility.

Workarounds

• Implement network segmentation to isolate Aterm Series devices from untrusted network segments
• Configure firewall rules to restrict management interface access to specific trusted IP addresses only
• Disable remote management features if not required for operational purposes
• Deploy a web application firewall (WAF) or reverse proxy with command injection filtering capabilities in front of device management interfaces where feasible

# Example firewall rule to restrict management access (adjust for your environment)
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP