CVE-2026-1460: Zyxel DX3301/EX3301 RCE Vulnerability

CVE-2026-1460 Overview

A post-authentication command injection vulnerability exists in the "DomainName" parameter of the DHCP configuration file in Zyxel DX3301-T0 and EX3301-T0 firmware versions through 5.50(ABVY.7.1)C0. This vulnerability could allow an authenticated attacker with administrator privileges to execute arbitrary OS commands on an affected device.

Critical Impact

Authenticated attackers with administrative access can achieve full operating system command execution, potentially leading to complete device compromise, network reconnaissance, lateral movement, and persistent access to affected Zyxel network infrastructure.

Affected Products

• Zyxel DX3301-T0 firmware versions through 5.50(ABVY.7.1)C0
• Zyxel EX3301-T0 firmware versions through 5.50(ABVY.7.1)C0

Discovery Timeline

• April 28, 2026 - CVE-2026-1460 published to NVD
• April 28, 2026 - Last updated in NVD database

Technical Details for CVE-2026-1460

Vulnerability Analysis

This command injection vulnerability (CWE-78) occurs within the DHCP configuration functionality of affected Zyxel CPE devices. The vulnerability exists due to improper sanitization of the "DomainName" parameter when processing DHCP configuration file changes. When an administrator modifies this setting through the device's management interface, user-supplied input is passed to underlying system functions without adequate validation or escaping.

The flaw requires administrative authentication to exploit, meaning an attacker must first obtain valid administrator credentials. However, once authenticated, the attacker can inject arbitrary shell commands that execute with the privileges of the underlying operating system, typically root-level access on embedded Linux-based network devices.

Root Cause

The root cause is insufficient input validation and sanitization of the "DomainName" parameter within the DHCP configuration handler. The parameter value is likely passed directly to shell commands or system calls without proper escaping or validation against command injection metacharacters. Special characters commonly used in command injection attacks (such as ;, |, $(), and backticks) are not filtered before being processed by the system shell.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated administrative access to the device's management interface. The attack flow involves:

1. Attacker gains or compromises administrator credentials for the target Zyxel device
2. Attacker accesses the DHCP configuration settings through the web management interface
3. Attacker crafts a malicious "DomainName" parameter value containing command injection payloads
4. The injected commands execute with system privileges when the configuration is processed

Due to the administrative privilege requirement, this vulnerability would typically be exploited as part of a targeted attack chain, following initial credential theft or compromise. The vulnerability mechanism involves injecting OS commands through the DomainName parameter in DHCP configuration. Attackers can append shell metacharacters and commands to execute arbitrary code on the underlying system. For detailed technical information, refer to the Zyxel Security Advisory.

Detection Methods for CVE-2026-1460

Indicators of Compromise

• Unusual processes spawned by the device's web server or configuration services
• Unexpected outbound network connections from the Zyxel device
• Modified system files or unauthorized user accounts on the device
• Anomalous entries in device logs showing unusual DomainName parameter values containing shell metacharacters

Detection Strategies

• Monitor DHCP configuration changes for suspicious DomainName values containing special characters (;, |, $, backticks)
• Implement network-based monitoring for unexpected outbound connections from Zyxel devices
• Enable enhanced logging on device management interfaces to capture configuration modification attempts
• Deploy intrusion detection rules to identify command injection patterns in HTTP traffic to device management ports

Monitoring Recommendations

• Enable and centralize logging from all Zyxel CPE devices for security monitoring
• Monitor administrative login activity for anomalous access patterns or credential abuse
• Track firmware versions across deployed devices to ensure timely patching
• Implement network segmentation to limit the impact of compromised edge devices

How to Mitigate CVE-2026-1460

Immediate Actions Required

• Review and apply the latest firmware updates from Zyxel that address this vulnerability
• Audit administrative account credentials and implement strong password policies
• Restrict management interface access to trusted IP addresses only
• Review device logs for signs of prior exploitation attempts
• Consider disabling remote management access until patching is complete

Patch Information

Zyxel has released a security advisory addressing this command injection vulnerability. Organizations should review the Zyxel Security Advisory for Command Injection and apply the recommended firmware updates to all affected DX3301-T0 and EX3301-T0 devices.

Workarounds

• Restrict administrative access to the device management interface to trusted internal networks only
• Implement network ACLs to block external access to device management ports
• Use a VPN for remote administration instead of exposing the management interface directly
• Consider deploying additional network monitoring to detect exploitation attempts

# Example: Restrict management interface access via firewall rules
# Block external access to management interface (typical ports)
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

# Allow management access only from specific admin workstation
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.100 -j ACCEPT