CVE-2020-9054 Information

Description

Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21 contain a pre-authentication command injection vulnerability which may allow a remote unauthenticated attacker to execute arbitrary code on a vulnerable device. ZyXEL NAS devices achieve authentication by using the weblogin.cgi CGI executable. This program fails to properly sanitize the username parameter that is passed to it. If the username parameter contains certain characters it can allow command injection with the privileges of the web server that runs on the ZyXEL device. Although the web server does not run as the root user ZyXEL devices include a setuid utility that can be leveraged to run any command with root privileges. As such it should be assumed that exploitation of this vulnerability can lead to remote code execution with root privileges. By sending a specially-crafted HTTP POST or GET request to a vulnerable ZyXEL device a remote unauthenticated attacker may be able to execute arbitrary code on the device. This may happen by directly connecting to a device if it is directly exposed to an attacker. However there are ways to trigger such crafted requests even if an attacker does not have direct connectivity to a vulnerable devices. For example simply visiting a website can result in the compromise of any ZyXEL device that is reachable from the client system. Affected products include: NAS326 before firmware V5.21(AAZF.7)C0 NAS520 before firmware V5.21(AASZ.3)C0 NAS540 before firmware V5.21(AATB.4)C0 NAS542 before firmware V5.21(ABAG.4)C0 ZyXEL has made firmware updates available for NAS326 NAS520 NAS540 and NAS542 devices. Affected models that are end-of-support: NSA210 NSA220 NSA220+ NSA221 NSA310 NSA310S NSA320 NSA320S NSA325 and NSA325v2

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Reference

https://cwe.mitre.org/data/definitions/78.html https://kb.cert.org/artifacts/cve-2020-9054.html https://kb.cert.org/vuls/id/498544/ https://krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-devices/ https://www.zyxel.com/support/remote-code-execution-vulnerability-of-NAS-products.shtml

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

9.8