--- title: "CVE-2020-9054: ZyXEL NAS products running firmware… | CubePath" description: "Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21 contain a pre-authentication command injection vulnerability…" language: en source: https://cubepath.com/security/cve/CVE-2020-9054 --- # CVE-2020-9054: ZyXEL NAS products running firmware… | CubePath ## 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 Official description from the CVE record, published by certcc. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2020-9054) ## Key data ### CVSS 3.1 Critical 9.8 Score published by CISA-ADP in the CVE record. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | Metric | Value | What it means | | ---------------------- | --------- | ----------------------------------------------------------------------------------- | | Attack vector | Network | The vulnerable component can be reached over a network, possibly from the Internet. | | Attack complexity | Low | No special conditions are needed. The attack can be repeated at will. | | Privileges required | None | No account or privileges are needed. | | User interaction | None | No action from any user is needed. | | Scope | Unchanged | The impact stays within the vulnerable component. | | Confidentiality impact | High | Serious or total effect on the secrecy of data. | | Integrity impact | High | Serious or total effect on the trustworthiness of data. | | Availability impact | High | Serious or total effect on availability. | CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at [first.org/cvss](https://www.first.org/cvss/) . ### EPSS Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days. Score 0.99988 (99.98% probability) Percentile 99.98% Scores of Nov 10, 2026 Model v2026.06.15 ### CISA Known Exploited Vulnerabilities This CVE is listed in the CISA KEV catalog. Name in the catalog Zyxel Multiple NAS Devices OS Command Injection Vulnerability Added to the catalog Mar 25, 2022 Federal due date Apr 15, 2022 ### CISA assessment as of Feb 7, 2025 Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA. Exploitation Recorded by CISA as active Automatable no Technical impact total ### Weakness (CWE) CWE catalog version 5.0. CWE names: Copyright © 2006-2026, The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CWE license. - [CWE-78](https://cwe.mitre.org/data/definitions/78.html) Improper Neutralization of Special Elements used in an OS Command ## Affected products Products listed in the CVE record, as the CNA published them. - ZyXEL NAS326 - affected: V5.21(AAZF.7)C0 up to V5.21(AAZF.7)C0 - ZyXEL NAS520 - affected: V5.21(AASZ.3)C0 up to V5.21(AASZ.3)C0 - ZyXEL NAS540 - affected: V5.21(AATB.4)C0 up to V5.21(AATB.4)C0 - ZyXEL NAS542 - affected: V5.21(ABAG.4)C0 up to V5.21(ABAG.4)C0 - ZyXEL NSA210 - affected: all - ZyXEL NSA220 - affected: all - ZyXEL NSA220+ - affected: all - ZyXEL NSA221 - affected: all - ZyXEL NSA310 - affected: V4.75(AALH.2)C0 up to V4.75(AALH.2)C0 - ZyXEL NSA320 - affected: all - ZyXEL NSA320S - affected: V4.75(AANV.2)C0 up to V4.75(AANV.2)C0 - ZyXEL NSA325 - affected: V4.81(AAAJ.1)C0 up to V4.81(AAAJ.1)C0 - ZyXEL NSA325v2 - affected: V4.81(AALS.1)C0 up to V4.81(AALS.1)C0 ## References Links listed in the CVE record. They lead to other sites, which CubePath does not control. - [cwe.mitre.org/data/definitions/78.html](https://cwe.mitre.org/data/definitions/78.html) - [zyxel.com/support/remote-code-execution-vulnerability-of-NA…](https://www.zyxel.com/support/remote-code-execution-vulnerability-of-NAS-products.shtml) - [VU#498544](https://kb.cert.org/vuls/id/498544/) (kb.cert.org) third-party-advisory - [kb.cert.org/artifacts/cve-2020-9054.html](https://kb.cert.org/artifacts/cve-2020-9054.html) - [krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-sto…](https://krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-devices/) ## Timeline 1. ID reserved Feb 18, 2020 2. Record published Mar 4, 2020 3. Added to CISA KEV Mar 25, 2022 4. Record last updated Oct 7, 2026 ## Look up another CVE ## About CubePath CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection. [Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection) Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:31 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)