CVE-2024-9200 Overview
CVE-2024-9200 is a post-authentication command injection vulnerability affecting multiple Zyxel customer premises equipment (CPE) devices, including DSL, fiber, and Wi-Fi extender products. The flaw resides in the host parameter of the diagnostic function exposed by the device management interface. An authenticated attacker with administrator privileges can inject arbitrary operating system commands that execute in the context of the underlying firmware. The issue is tracked under CWE-78: OS Command Injection and was disclosed in the Zyxel Security Advisory published December 3, 2024.
Critical Impact
An authenticated administrator can achieve arbitrary OS command execution on affected Zyxel CPE devices, potentially pivoting into the connected customer network.
Affected Products
- Zyxel VMG4005-B50A, VMG4005-B60A, and VMG4005-B50B firmware through V5.15(ABQA.2.2)C0
- Zyxel VMG3927-B50B and VMG4927-B50A firmware
- Zyxel EMG6726-B10A firmware
Discovery Timeline
- 2024-12-03 - Zyxel publishes security advisory covering buffer overflow and post-authentication command injection issues in CPE devices
- 2024-12-03 - CVE-2024-9200 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-9200
Vulnerability Analysis
The vulnerability exists in the diagnostic function of the affected Zyxel CPE firmware. The host parameter, typically used to accept a hostname or IP address for network diagnostic operations such as ping or traceroute, is passed to an underlying OS command without adequate sanitization. Attackers who supply shell metacharacters within this parameter can break out of the intended command and execute arbitrary instructions.
Exploitation requires prior authentication with administrator privileges, which reduces the population of attackers capable of reaching the vulnerable code path. However, embedded CPE devices frequently retain default or weak administrator credentials, and internet-exposed management interfaces broaden the risk surface. The EPSS probability is 1.134% (63.5th percentile) as of August 2026.
Root Cause
The root cause is improper neutralization of special elements used in an OS command [CWE-78]. The diagnostic handler concatenates user-controlled input from the host field directly into a shell invocation. Because shell metacharacters such as ;, |, &, and backticks are not filtered or escaped, injected payloads execute alongside the intended diagnostic command.
Attack Vector
An authenticated administrator sends a crafted request to the diagnostic endpoint of the web management interface. The host field carries an appended shell command separated by a metacharacter. The device executes the injected command with the privileges of the diagnostic process, which on typical Zyxel CPE firmware runs as root. Successful exploitation yields firmware-level command execution, enabling persistence, configuration tampering, or lateral movement into the customer LAN. No verified proof-of-concept has been published for this CVE.
Detection Methods for CVE-2024-9200
Indicators of Compromise
- Administrator-authenticated HTTP or HTTPS requests to the diagnostic endpoint containing shell metacharacters (;, |, &, `, $() in the host parameter
- Unexpected outbound connections originating from CPE devices to attacker-controlled infrastructure
- Unauthorized modifications to device configuration, DNS settings, or firmware after administrator login events
Detection Strategies
- Inspect device management logs for diagnostic function invocations with unusual host parameter values that do not resemble hostnames or IP addresses
- Correlate administrator login events with subsequent diagnostic requests and outbound traffic anomalies from the CPE
- Monitor for firmware version strings matching vulnerable builds through network asset inventory scans
Monitoring Recommendations
- Forward CPE syslog and management interface logs into a centralized SIEM for behavioral analysis
- Alert on administrator authentication attempts from non-management network segments
- Track configuration checksums and firmware hashes to detect unauthorized changes on ISP-managed devices
How to Mitigate CVE-2024-9200
Immediate Actions Required
- Apply the firmware updates published in the Zyxel Security Advisory for each affected model
- Rotate administrator credentials on all CPE devices and remove any shared or default accounts
- Restrict access to the device management interface to trusted management VLANs only
Patch Information
Zyxel released firmware updates addressing CVE-2024-9200 alongside related buffer overflow and command injection issues on December 3, 2024. Refer to the vendor advisory for the specific fixed firmware version corresponding to each affected model, including VMG4005-B50A, VMG4005-B60A, VMG4005-B50B, VMG3927-B50B, VMG4927-B50A, and EMG6726-B10A.
Workarounds
- Disable remote administration on the WAN interface and enforce local-only management until patches are deployed
- Place CPE management interfaces behind a jump host or VPN to eliminate direct exposure
- Enforce strong, unique administrator passwords and enable account lockout to raise the barrier for pre-conditions of exploitation
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
