Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2020-9054

CVE-2020-9054CRITICAL

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

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS    %ile   KEV
   N   L   N   N  U  H  H  H    9.8   .9999   100.0   YES

AFFECTED
  Product  Versions           Fixed
  NAS326   V5.21(AAZF.7)C0 –  —
  NAS520   V5.21(AASZ.3)C0 –  —
  NAS540   V5.21(AATB.4)C0 –  —
  NAS542   V5.21(ABAG.4)C0 –  —
  NSA210   all –              —
  NSA220   all –              —
  NSA220+  all –              —
  NSA221   all –              —
  NSA310   V4.75(AALH.2)C0 –  —
  NSA320   all –              —
  + 3 more

TIMELINE
  Feb 18  Reserved by certcc
  Mar 4   Published (CNA: certcc)
  Mar 25  Added to CISA KEV, remediation due 2022-04-15

CWE-78 · CNA: certcc · CVSS v3.1 · 6 references · KEV due April 15, 2022

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

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
February 18, 2020	Reserved	Reserved by certcc
March 4, 2020	Published	Published (CNA: certcc)
March 25, 2022	KEV ADDED	Added to CISA KEV, remediation due 2022-04-15

Affected

Affected products and packages — 13 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
ZyXEL	NAS326	—	V5.21(AAZF.7)C0	—
ZyXEL	NAS520	—	V5.21(AASZ.3)C0	—
ZyXEL	NAS540	—	V5.21(AATB.4)C0	—
ZyXEL	NAS542	—	V5.21(ABAG.4)C0	—
ZyXEL	NSA210	—	all	—
ZyXEL	NSA220	—	all	—
ZyXEL	NSA220+	—	all	—
ZyXEL	NSA221	—	all	—
ZyXEL	NSA310	—	V4.75(AALH.2)C0	—
ZyXEL	NSA320	—	all	—
ZyXEL	NSA320S	—	V4.75(AANV.2)C0	—
ZyXEL	NSA325	—	V4.81(AAAJ.1)C0	—
ZyXEL	NSA325v2	—	V4.81(AALS.1)C0	—

Weaknesses

CWE-78

References (6)

https://cwe.mitre.org/data/definitions/78.html [x_refsource_MISC]
https://kb.cert.org/artifacts/cve-2020-9054.html [x_refsource_MISC]
https://kb.cert.org/vuls/id/498544/ [third-party-advisory, x_refsource_CERT-VN]
https://krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-devices/ [x_refsource_MISC]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-9054 [government-resource]
https://www.zyxel.com/support/remote-code-execution-vulnerability-of-NAS-products.shtml [x_refsource_CONFIRM]

Authoritative record: CVE-2020-9054 at cve.org

Vendors: zyxel

Weaknesses: CWE-78

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2020-9054 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.