CVE-2024-9200 Overview
CVE-2024-9200 is a post-authentication command injection vulnerability affecting multiple Zyxel customer-premises equipment (CPE) devices. The flaw resides in the host parameter of the diagnostic function in Zyxel VMG4005-B50A firmware versions through V5.15(ABQA.2.2)C0 and related product lines. An authenticated attacker with administrator privileges can inject operating system commands and execute them on the underlying device. The vulnerability is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command.
Critical Impact
Successful exploitation grants an authenticated administrator full command execution on the router's operating system, enabling persistence, traffic interception, and pivoting into internal networks.
Affected Products
- Zyxel VMG4005-B50A, VMG4005-B60A, 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 - CVE-2024-9200 published to NVD alongside Zyxel security advisory
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-9200
Vulnerability Analysis
The vulnerability exists in the diagnostic function exposed through the device's administrative web interface. This function accepts a host parameter, typically used to specify a target for network diagnostic operations such as ping or traceroute. The application passes this parameter to an operating system shell without proper neutralization of shell metacharacters.
An authenticated administrator can supply crafted input containing shell separators such as ;, |, &&, or backticks. The router's underlying shell interprets the appended payload as additional commands, executing them with the privileges of the diagnostic process. On embedded Linux-based CPE devices, this typically means root-level execution.
Because exploitation requires administrator credentials, the attack surface is limited to scenarios where credentials are weak, default, reused, or already compromised. However, once achieved, the attacker gains full control of the device.
Root Cause
The root cause is missing input validation and unsafe command construction in the diagnostic handler. User-controlled data flows directly into a shell command string without sanitization or the use of parameterized process execution APIs, satisfying the pattern described in [CWE-78].
Attack Vector
Exploitation requires network access to the device management interface and valid administrator credentials. The attacker submits a diagnostic request in which the host field contains an appended shell command. The device concatenates the input into a shell invocation and executes the injected commands. No user interaction is required beyond the attacker's own authenticated session. See the Zyxel security advisory for vendor-confirmed technical details.
Detection Methods for CVE-2024-9200
Indicators of Compromise
- Diagnostic requests containing shell metacharacters such as ;, |, &, $(, or backticks in the host parameter.
- Unexpected outbound connections originating from the router to unfamiliar external hosts.
- New processes or cron entries appearing on the device after administrator login events.
- Configuration changes to DNS, firewall, or routing tables that do not correspond to authorized operator activity.
Detection Strategies
- Inspect web server and management-interface logs for diagnostic function invocations containing non-hostname characters in the host field.
- Correlate administrator authentication events with subsequent diagnostic requests to identify anomalous automation patterns.
- Alert on multiple failed administrator logins followed by successful authentication and immediate diagnostic activity.
Monitoring Recommendations
- Forward router syslog and management logs to a centralized SIEM for retention and correlation.
- Monitor DNS traffic from the router itself for command-and-control indicators, since a compromised router can act as a stealthy pivot.
- Track firmware versions across the fleet to identify devices still running vulnerable builds through or below V5.15(ABQA.2.2)C0.
How to Mitigate CVE-2024-9200
Immediate Actions Required
- Apply the firmware updates published in the Zyxel security advisory for each affected model.
- Rotate all administrator credentials on affected devices after patching.
- Disable WAN-side access to the management interface if it is not required for operations.
Patch Information
Zyxel released patched firmware for the affected VMG4005-B50A, VMG4005-B60A, VMG4005-B50B, VMG3927-B50B, VMG4927-B50A, and EMG6726-B10A product lines. Refer to the vendor advisory for the specific fixed firmware version applicable to each model and region.
Workarounds
- Restrict administrative access to the device to trusted management VLANs or IP ranges using ACLs.
- Enforce strong, unique administrator passwords and multi-factor authentication where the device supports it.
- Segment CPE devices from sensitive internal networks so that a compromised router cannot directly reach critical assets.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
