CVE-2020-9054 — Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5

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 authent

01What is this vulnerability?

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…

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2022-03-25. Ransomware use: Unknown.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

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07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-03-04T20:15:10.750
• Last modified: 2026-10-08T13:38:30.407
• Added to CISA KEV: 2022-03-25

09References

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