Zyxel firewall and VPN devices affected by critical flaws

Zyxel fixed two critical flaws in multiple firewall and VPN products that can lead to remote code execution or cause a DoS condition.

Zyxel addressed two critical buffer overflow vulnerabilities, tracked as CVE-2023-33009 and CVE-2023-33010, that affect several of its firewall and VPN products.

A remote, unauthenticated attacker can can trigger the flaws to cause a denial-of-service (DoS) condition and remote code execution on vulnerable devices.

Below are the description for both issues provided by the vendor in a security advisory:

CVE-2023-33009 – A buffer overflow vulnerability in the notification function in some firewall versions could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device. CVE-2023-33010 – A buffer overflow vulnerability in the ID processing function in some firewall versions could allow an unauthenticated attacker to cause DoS conditions and even a remote code execution on an affected device

Users are recommended to install security updates provided by the company to address the issues.

CVE-2023-33009: A buffer overflow vulnerability in the notification function in some Zyxel products, allowing an unauthenticated attacker to perform remote code execution or impose DoS conditions. (critical severity score of 9.8) CVE-2023-33010: A buffer overflow vulnerability in the ID processing function in some Zyxel products, allowing an unauthenticated attacker to perform remote code execution or impose DoS conditions. (critical severity score of 9.8)

The following table includes vulnerable devices:

Affected seriesAffected versionPatch availability

ATP	ZLD V4.32 to V5.36 Patch 1	ZLD V5.36 Patch 2
USG FLEX	ZLD V4.50 to V5.36 Patch 1	ZLD V5.36 Patch 2
USG FLEX50(W) / USG20(W)-VPN	ZLD V4.25 to V5.36 Patch 1	ZLD V5.36 Patch 2
VPN	ZLD V4.30 to V5.36 Patch 1	ZLD V5.36 Patch 2
ZyWALL/USG	ZLD V4.25 to V4.73 Patch 1	ZLD V4.73 Patch 2

At the end April, Zyxel fixed a critical RCE flaw, tracked as CVE-2023-28771 (CVSS score 9.8), in its firewall devices and urged customers to install the patches.

The company also fixed a high-severity post-authentication command injection issue (CVE-2023-27991, CVSS score: 8.8) affecting some specific firewall versions.

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Pierluigi Paganini

(SecurityAffairs – hacking, Zyxel)

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