CVE-2019-15804 : Exploit Details and Defense Strategies

A vulnerability has been found on Zyxel GS1900 devices running firmware versions prior to 2.50(AAHH.0)C0. By sending a signal to the CLI process, it activates a feature that was not documented. The SIGQUIT signal sent to the CLI application triggers a menu, including options for 'Password recovery for specific user.' Access to this menu is prevented by an access control check, but it is suspected that it can be accessed using a serial console.

Understanding CVE-2019-15804

This CVE identifies a security issue in Zyxel GS1900 devices that could potentially allow unauthorized access to a hidden menu.

What is CVE-2019-15804?

The vulnerability in Zyxel GS1900 devices allows unauthorized access to a hidden menu by triggering an undocumented feature through the CLI process.

The Impact of CVE-2019-15804

The vulnerability could lead to unauthorized users accessing sensitive options like 'Password recovery for specific user,' compromising device security.

Technical Details of CVE-2019-15804

This section provides technical insights into the vulnerability.

Vulnerability Description

Sending a SIGQUIT signal to the CLI process on Zyxel GS1900 devices triggers a hidden menu with potentially sensitive options.

Affected Systems and Versions

Affected devices: Zyxel GS1900 devices
Vulnerable firmware versions: Prior to 2.50(AAHH.0)C0

Exploitation Mechanism

Triggering the hidden menu by sending a SIGQUIT signal to the CLI application
Accessing the menu, including 'Password recovery for specific user' options, via a serial console

Mitigation and Prevention

Protect your systems from CVE-2019-15804 with these mitigation strategies.

Immediate Steps to Take

Update affected Zyxel GS1900 devices to firmware version 2.50(AAHH.0)C0 or newer
Monitor and restrict access to CLI processes

Long-Term Security Practices

Regularly review and update access control policies
Conduct security audits to identify and address potential vulnerabilities

Patching and Updates

Stay informed about security advisories from Zyxel
Apply patches and updates promptly to address known vulnerabilities