CVE-2026-4619: NEC Aterm Path Traversal Vulnerability

CVE-2026-4619 Overview

CVE-2026-4619 is a Path Traversal vulnerability affecting NEC Platforms, Ltd. Aterm Series network devices. This vulnerability allows an attacker to write over any file on the affected device via network access, potentially leading to system compromise, configuration tampering, or complete device takeover.

Critical Impact

Authenticated attackers with network access can exploit improper path validation to overwrite arbitrary files on vulnerable NEC Aterm Series devices, potentially leading to persistent compromise or denial of service.

Affected Products

• NEC Platforms, Ltd. Aterm Series devices

Discovery Timeline

• 2026-03-27 - CVE-2026-4619 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2026-4619

Vulnerability Analysis

This Path Traversal vulnerability (CWE-22) exists in NEC Aterm Series network devices. The flaw allows attackers to bypass intended directory restrictions and write files to arbitrary locations on the filesystem. While the vulnerability requires high privileges and involves some attack complexity, successful exploitation can result in significant impacts to the integrity and availability of affected devices.

The vulnerability enables file overwrite capabilities, which could be leveraged to replace critical system files, configuration files, or firmware components. This type of attack is particularly dangerous in network equipment as it could allow attackers to establish persistence, modify device behavior, or render devices inoperable.

Root Cause

The vulnerability stems from insufficient validation of user-supplied file paths within the Aterm Series firmware. When processing file operations, the application fails to properly sanitize path components containing directory traversal sequences such as ../ or encoded variants. This improper input validation allows attackers to escape the intended directory and access the broader filesystem.

Attack Vector

Exploitation requires network access to the vulnerable device along with elevated privileges. An attacker must first authenticate to the device with appropriate credentials before they can leverage the path traversal flaw. The attack does not require user interaction, making it suitable for automated exploitation once initial access is obtained.

The attacker crafts a malicious request containing directory traversal sequences in file path parameters. These sequences navigate outside the intended directory structure, allowing the attacker to specify arbitrary file locations for write operations. The device processes these requests without adequate path sanitization, resulting in unintended file overwrites.

Detection Methods for CVE-2026-4619

Indicators of Compromise

• Unexpected modifications to system configuration files or firmware on Aterm Series devices
• Unusual file write operations in system logs, particularly those containing path traversal patterns (../, ..%2f, etc.)
• Authentication logs showing privileged access from unfamiliar IP addresses or at unusual times
• Integrity check failures on critical system files

Detection Strategies

• Implement file integrity monitoring (FIM) on critical configuration and system files on network devices
• Monitor network traffic for requests containing directory traversal patterns targeting Aterm management interfaces
• Deploy intrusion detection signatures to identify path traversal attack patterns in HTTP requests
• Review authentication logs regularly for anomalous privileged access patterns

Monitoring Recommendations

• Enable comprehensive logging on Aterm Series devices and forward logs to a centralized SIEM
• Configure alerts for any file system modifications outside expected operational patterns
• Monitor administrative interface access and correlate with authorized change windows
• Implement network segmentation to limit exposure of device management interfaces

How to Mitigate CVE-2026-4619

Immediate Actions Required

• Review the NEC Security Advisory NV26-001 for specific affected models and remediation guidance
• Restrict network access to device management interfaces to trusted administrative networks only
• Audit and limit accounts with elevated privileges on affected devices
• Implement network-level access controls to prevent unauthorized connections to vulnerable interfaces

Patch Information

NEC Platforms, Ltd. has released security guidance for this vulnerability. Administrators should consult the official NEC Security Advisory NV26-001 for detailed information on affected firmware versions and available updates. Apply vendor-supplied patches or firmware updates as soon as they become available.

Workarounds

• Restrict management interface access to trusted IP addresses using firewall rules or access control lists
• Disable remote management if not required for operational purposes
• Place affected devices behind a VPN requiring additional authentication
• Monitor and audit all privileged operations on affected devices until patches can be applied

# Example: Restrict management access on network firewall
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP