CVE-2020-9054: Zyxel Multiple NAS Devices OS Command Injection Vulnerability

CISA Known Exploited Vulnerabilities

Name

Zyxel Multiple NAS Devices OS Command Injection Vulnerability

Vendor

Zyxel

Product

Multiple Network-Attached Storage (NAS) Devices

Added to the catalog

2022-03-25

Due date for US federal agencies

2022-04-15

Weaknesses

CWE-78

Catalog version

2026.10.30

Multiple Zyxel network-attached storage (NAS) devices contain a pre-authentication command injection vulnerability, which may allow a remote, unauthenticated attacker to execute arbitrary code.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://nvd.nist.gov/vuln/detail/CVE-2020-9054

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2020-03-04T20:15:10.750

Last modified

2026-10-08T13:38:30.407

Weaknesses

CWE-78

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

References

• https://cwe.mitre.org/data/definitions/78.html (Third Party Advisory)
• https://kb.cert.org/artifacts/cve-2020-9054.html (Third Party Advisory, US Government Resource)
• https://kb.cert.org/vuls/id/498544/ (Third Party Advisory, US Government Resource)
• https://krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-devices/ (Exploit, Third Party Advisory)
• https://www.zyxel.com/support/remote-code-execution-vulnerability-of-NAS-products.shtml (Vendor Advisory)
• https://cwe.mitre.org/data/definitions/78.html (Third Party Advisory)
• https://kb.cert.org/artifacts/cve-2020-9054.html (Third Party Advisory, US Government Resource)
• https://kb.cert.org/vuls/id/498544/ (Third Party Advisory, US Government Resource)
• https://krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-devices/ (Exploit, Third Party Advisory)
• https://www.zyxel.com/support/remote-code-execution-vulnerability-of-NAS-products.shtml (Vendor Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-9054 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:43.468Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2020-9054

CVE record

Title (CNA)

ZyXEL NAS products running firmware version 5.21 and earlier are vulnerable to pre-authentication command injection in weblogin.cgi

Assigner

certcc

State

PUBLISHED

Published

2020-03-04T19:30:18.400Z

Updated

2026-10-07T17:32:05.389Z

Problem types

CWE-78 OS Command Injection

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

References

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

Read on 2026-11-03T01:05:16.579Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2020/9xxx/CVE-2020-9054.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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