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CVE-2020-9054

9.8, critical Known exploited

Zyxel Multiple NAS Devices OS Command Injection Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
9.8, critical critical CVSS v3.1
EPSS, next 30 days
100% higher than 99.9% of scored CVEs
Exploitation
Confirmed in the wild
Published
4 Mar 20206 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 25 Mar 2022. US federal agencies had to remediate by 15 Apr 2022, a deadline that has passed.

Required action. Apply updates per vendor instructions.

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

Details

Vendor
Zyxel
Product
NAS326
Weakness
CWE-78 (opens in a new tab)
Status
Analyzed
Updated
8 Oct 2026
Assigner
cret@cert.org

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

References 6

Exploit code 1

Advisories 4

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Zyxel CVEs

Every Zyxel CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-7273 Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability KEV EPSS 3% 8.8, high
  • CVE-2024-40890 Zyxel DSL CPE OS Command Injection Vulnerability KEV EPSS 21% 8.8, high
  • CVE-2024-40891 Zyxel DSL CPE OS Command Injection Vulnerability KEV EPSS 22% 8.8, high
  • CVE-2024-11667 Zyxel Multiple Firewalls Path Traversal Vulnerability KEV EPSS 3% 9.8, critical
  • CVE-2023-27992 Zyxel Multiple NAS Devices Command Injection Vulnerability KEV EPSS 83% 9.8, critical
  • CVE-2023-33009 Zyxel Multiple Firewalls Buffer Overflow Vulnerability KEV EPSS 28% 9.8, critical
  • CVE-2023-33010 Zyxel Multiple Firewalls Buffer Overflow Vulnerability KEV EPSS 29% 9.8, critical
  • CVE-2023-28771 Zyxel Multiple Firewalls OS Command Injection Vulnerability KEV EPSS 99% 9.8, critical

Beyond this page

Is CVE-2020-9054 in your network?

This page tells you how dangerous CVE-2020-9054 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2020-9054 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

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Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.