CVE-2024-12009: Zyxel Dx3300-t0 Firmware RCE Vulnerability

CVE-2024-12009 Overview

CVE-2024-12009 is a post-authentication command injection vulnerability in the ZyEE function of multiple Zyxel DSL, Ethernet CPE, Fiber ONT, and WiFi extender devices. The flaw affects the Zyxel EX5601-T1 firmware version V5.70(ACDZ.3.6)C0 and earlier, along with a broad range of related product lines. An authenticated attacker holding administrator privileges can leverage the flaw to execute arbitrary operating system commands on a vulnerable device. The weakness is classified under CWE-78, improper neutralization of special elements used in an OS command.

Critical Impact
Successful exploitation grants command execution on the underlying operating system of the CPE, giving an administrator-level attacker full control over routing, DNS, and traffic inspection on the device.

Affected Products

Zyxel EX5601-T1 firmware V5.70(ACDZ.3.6)C0 and earlier
Zyxel DSL and Ethernet CPE families including DX3300, DX3301, DX4510, DX5401, EX3300, EX3301, EX3500, EX3501, EX3510, EX3600, EX5401, EX5501, EX5510, EX5512, EX5601, EX7501, EX7710
Zyxel Fiber ONT and WiFi extender families including EE6510, EMG3525, EMG5523, EMG5723, VMG3625, VMG3927, VMG8623, VMG8825, AX7501, PX3321, PX5301, WX5600, WX5610

Discovery Timeline

2025-03-11 - Zyxel publishes security advisory for post-authentication command injection vulnerabilities in DSL, Ethernet CPE, Fiber ONT, and WiFi extender devices
2025-03-11 - CVE-2024-12009 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-12009

Vulnerability Analysis

The vulnerability resides in the ZyEE function exposed by the device management interface. This function fails to properly neutralize special shell metacharacters supplied through administrator-accessible parameters. When an authenticated administrator submits crafted input, the underlying handler concatenates the value into a system command string that is passed to a shell interpreter.

Because exploitation is possible over the network and requires no user interaction, an attacker with valid administrator credentials, whether stolen, guessed, or obtained through default credentials, can convert an authenticated session into full OS command execution. The impact spans confidentiality, integrity, and availability of the device.

Root Cause

The root cause is improper neutralization of special elements used in an OS command ([CWE-78]). The ZyEE handler treats attacker-influenced input as part of a shell command line rather than as data passed to a safely-invoked binary. Missing input validation and unsafe command construction allow metacharacters such as ;, |, &, and backticks to break out of the intended command context.

Attack Vector

Exploitation follows a straightforward path. The attacker first authenticates to the device web interface or management API with administrator credentials. The attacker then issues a request that invokes the ZyEE function with a parameter containing embedded shell commands. The device shell executes both the intended command and the injected payload with the privileges of the management process, typically root on embedded Linux CPEs. Post-exploitation activity commonly includes persistent backdoor installation, DNS tampering, credential theft from device configuration, and pivoting into the internal network segment served by the CPE.

// No verified public proof-of-concept is available.
// Refer to the Zyxel security advisory for technical remediation guidance.

Detection Methods for CVE-2024-12009

Indicators of Compromise

Administrator authentication events from unexpected source IP addresses immediately followed by requests targeting the ZyEE function or related management endpoints
Outbound connections from the CPE to unfamiliar hosts, particularly to package repositories, pastebins, or IRC/C2 infrastructure
Unexpected processes, cron entries, or startup scripts appearing on the device after firmware updates
Changes to DNS server settings, firewall rules, or port-forwarding entries that were not made by a legitimate administrator

Detection Strategies

Monitor management interface logs for administrator sessions issuing parameters containing shell metacharacters such as ;, |, &, $(, or backticks
Alert on any successful administrator login from outside the approved management network or from geographies inconsistent with normal operations
Correlate configuration change events with the account, source IP, and time window in which they occurred to detect abuse of legitimate administrator sessions

Monitoring Recommendations

Forward Zyxel device syslog and management-plane events to a centralized log platform for retention and correlation
Track outbound traffic from CPE management IP addresses; these devices should rarely initiate connections beyond DNS, NTP, and vendor update endpoints
Baseline expected administrator activity, including source networks and typical request patterns, and alert on deviations

How to Mitigate CVE-2024-12009

Immediate Actions Required

Apply the firmware updates published in the Zyxel security advisory for every affected model in the environment
Restrict the device web and remote management interfaces to trusted management networks only, and disable WAN-side management where it is not required
Rotate all administrator credentials on affected devices, and eliminate any default or shared passwords
Audit administrator accounts and remove any that are unused or unrecognized

Patch Information

Zyxel released fixed firmware alongside the advisory dated 2025-03-11. Administrators should consult the vendor advisory for the exact patched version applicable to each model. For the EX5601-T1, versions after V5.70(ACDZ.3.6)C0 contain the fix. Firmware versions for other affected models are enumerated in the advisory.

Workarounds

If firmware cannot be applied immediately, block administrator access from untrusted networks using ACLs on the device or upstream firewalls
Enforce strong, unique administrator passwords and enable multi-factor authentication on any management gateway that fronts the device
Disable remote management protocols such as TR-069 and HTTPS-WAN when they are not required for operations

bash

# Example: restrict device management to a trusted subnet upstream of the CPE
iptables -A FORWARD -p tcp -d <cpe_mgmt_ip> --dport 443 -s 10.10.20.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <cpe_mgmt_ip> --dport 443 -j DROP