CVE-2023-35138 : Security Advisory and Response

A command injection vulnerability in the "show_zysync_server_contents" function of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.

Understanding CVE-2023-35138

This CVE identifies a critical command injection vulnerability in Zyxel NAS326 and NAS542 firmware versions that could be exploited by an attacker to execute unauthorized OS commands.

What is CVE-2023-35138?

The vulnerability lies in the "show_zysync_server_contents" function of the affected firmware versions, enabling attackers to run malicious OS commands through specially crafted HTTP POST requests.

The Impact of CVE-2023-35138

If successfully exploited, the vulnerability can lead to unauthorized execution of arbitrary commands on the affected systems, potentially resulting in compromise of confidentiality, integrity, and availability of data.

Technical Details of CVE-2023-35138

The vulnerability is categorized with a CVSS v3.1 base score of 9.8 (Critical), indicating high severity with a low attack complexity and no privileges required for exploitation.

Vulnerability Description

CVE-2023-35138 is related to the improper neutralization of special elements used in an OS command, specifically an OS command injection flaw in Zyxel NAS326 and NAS542 firmware.

Affected Systems and Versions

Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 are confirmed to be affected by this vulnerability.

Exploitation Mechanism

An unauthenticated attacker can leverage this vulnerability by sending a well-crafted HTTP POST request to the "show_zysync_server_contents" function.

Mitigation and Prevention

To prevent exploitation and secure the affected systems, immediate actions and long-term security practices should be implemented.

Immediate Steps to Take

Update the firmware to the latest patched version provided by Zyxel.
Implement proper firewall rules to restrict unauthorized access to NAS devices.

Long-Term Security Practices

Regularly monitor security advisories from Zyxel for any new vulnerabilities.
Conduct periodic security audits to identify and mitigate potential risks.

Patching and Updates

Ensure timely installation of security patches and firmware updates released by Zyxel to address CVE-2023-35138 and other known vulnerabilities.