CVE-2021-35030 : What You Need to Know

A vulnerability was discovered in the Zyxel GS1900-8 firmware version 2.60, allowing an authenticated local user to launch a cross-site scripting (XSS) attack. This vulnerability was made public on July 27, 2021.

Understanding CVE-2021-35030

This section will delve into the specifics of CVE-2021-35030, including its impact and technical details.

What is CVE-2021-35030?

The CVE-2021-35030 vulnerability is related to improper handling of packet contents in the CGI program of Zyxel GS1900-8 firmware version 2.60. This flaw enables an authenticated local user to execute an XSS attack using a specially crafted LLDP packet.

The Impact of CVE-2021-35030

With a CVSS base score of 3.5, CVE-2021-35030 poses a low-severity threat. The vulnerability's impact is mainly on integrity and availability, with a low level of complexity for potential attackers.

Technical Details of CVE-2021-35030

In this section, we will discuss the vulnerability description, affected systems, and how the exploitation takes place.

Vulnerability Description

The vulnerability arises from inadequate sanitization of packet contents, which allows an authenticated local user to initiate a cross-site scripting attack via a specially crafted LLDP packet.

Affected Systems and Versions

The vulnerability affects Zyxel GS1900-8 firmware version 2.60. Users of this specific version are at risk of exploitation.

Exploitation Mechanism

An authenticated local user can exploit this vulnerability by sending a carefully crafted LLDP packet, triggering a cross-site scripting (XSS) attack on the targeted system.

Mitigation and Prevention

This section addresses the immediate steps to take and long-term security practices to safeguard against CVE-2021-35030.

Immediate Steps to Take

Upgrade the Zyxel GS1900-8 firmware to a patched version that addresses this vulnerability.
Regularly monitor and restrict access to the affected system to prevent unauthorized exploitation.

Long-Term Security Practices

Implement network segmentation to contain potential attacks and limit their impact.
Stay informed about security advisories from Zyxel and promptly apply recommended patches.

Patching and Updates

Zyxel has released a patched version of the GS1900-8 firmware to mitigate the CVE-2021-35030 vulnerability. Ensure all devices are updated to the latest firmware to prevent exploitation.