Reflected Cross-site Scripting In Zyxel ZyWALL

Title

Reflected Cross-Site Scripting

Product

Zyxel ZyWALL

Vulnerable Version

ZLD 4.30 and before

Fixed Version

ZLD 4.31

CVE Number

-

Impact

medium

Found

05.02.2018

By

T. Weber (Office Vienna) | SEC Consult Vulnerability Lab

Multiple Zyxel ZyWALL products with firmware 4.30 are affected by a reflected cross-site scripting vulnerability. Malicious JavaScript code can be executed in the browser of the user and session cookies can be stolen.

Vendor Description

Focused on innovation and customer-centricity, Zyxel Communications Corp. has been connecting people to the internet for nearly 30 years. We keep promoting creativity which meets the needs of customers. This spirit has never been changed since we developed the world’s first integrated 3-in-1 data/fax/voice modem in 1992. Our ability to adapt and innovate with networking technology
places us at the forefront of understanding connectivity for telco/service providers, businesses and home users.

We’re building the networks of tomorrow, helping unlock the world’s potential and meeting the needs of the modern workplace; powering people at work, life and play. We stand side-by-side with our customers and partners to share new approaches to networking that will unleash their abilities. Loyal friend, powerful ally, reliable resource — we are Zyxel, Your Networking Ally.”

Source: https://www.zyxel.com/about_zyxel/company_overview.shtml

Business Recommendation

SEC Consult recommends Zyxel customers to upgrade the firmware to the latest version available. A thorough security review should be performed by security professionals to identify further potential security issues.

1. Reflected Cross-Site Scripting (XSS)

A reflected cross-site scripting vulnerability was identified in ‘free_time_failed.cgi’ in the admin interface. The parameter ‘err_msg’ is returned without any sanitization of the input. An attacker, for example, can exploit this vulnerability to steal cookies from the attacked user in order to hijack a session and gain access to the device.

Proof Of Concept

1. Reflected Cross-Site Scripting (XSS)

By opening to the following link, contents of the ‘arip’ and ‘zy_pc_browser’ cookies will be displayed.

<IP-Address>/free_time_failed.cgi; <IP-Address>/free_time_failed.cgi;

 

Vulnerable / Tested Versions

The following versions are affected:

  • Zyxel ZyWall USG 110               ZLD 4.30 and earlier
  • Zyxel ZyWall USG 210               ZLD 4.30 and earlier
  • Zyxel ZyWall USG 310               ZLD 4.30 and earlier
  • Zyxel ZyWall USG 1100             ZLD 4.30 and earlier
  • Zyxel ZyWall USG 1900             ZLD 4.30 and earlier
  • Zyxel ZyWall USG 2200-VPN   ZLD 4.30 and earlier