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ExploitedIn CISA KEVFix available

CVE-2020-9054

Exploitation confirmed. First attested on 2022-03-25 by CISA-ADP, CISA KEV, GCVE · kevintel, GCVE · shadowserver.

  • Published2020-03-04
  • Fixed in4.35\(abps.3\)c0
  • WeaknessCWE-78

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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

Timeline

dates in UTC
  1. 2020-03-0420:15CVE publishedNVD
  2. 2022-03-25Added to the CISA KEV catalogCISA KEV
  3. 2022-03-25Listed as exploited by GCVEGCVE
  4. 2022-03-25Exploitation first reportedCISA KEV
  5. 2025-02-0713:09SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-9054?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-9054?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Zyxel atp100 firmwareversion to verify
BranchAffectedFixed in
4.35≥ 4.35, < 4.35\(abps.3\)c04.35\(abps.3\)c0
Zyxel atp200 firmwareversion to verify
BranchAffectedFixed in
4.35≥ 4.35, < 4.35\(abfw.3\)c04.35\(abfw.3\)c0
Zyxel atp500 firmwareversion to verify
BranchAffectedFixed in
4.35≥ 4.35, < 4.35\(abfu.3\)c04.35\(abfu.3\)c0

24 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA13 products

As certcc, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • ZyXEL NAS326
    Affected
    • ≥ V5.21(AAZF.7)C0, ≤ V5.21(AAZF.7)C0no fix statedcustom
  • ZyXEL NAS520
    Affected
    • ≥ V5.21(AASZ.3)C0, ≤ V5.21(AASZ.3)C0no fix statedcustom
  • ZyXEL NAS540
    Affected
    • ≥ V5.21(AATB.4)C0, ≤ V5.21(AATB.4)C0no fix statedcustom
  • ZyXEL NAS542
    Affected
    • ≥ V5.21(ABAG.4)C0, ≤ V5.21(ABAG.4)C0no fix statedcustom
  • ZyXEL NSA210
    Affected
    • all versionsno fix stated
  • ZyXEL NSA220
    Affected
    • all versionsno fix stated

7 more products in the CVE record.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2020-03-04

Fix

  1. Update Zyxel atp100 firmware to 4.35\(abps.3\)c0
  2. CISA’s required action: Apply updates per vendor instructions.due 2022-04-15

Advisories and patches

Detection

read 2026-11-02 22:42 UTC
Nuclei template
available
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifieddarrenmartyn/CVE-2020-9054
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

CISA Known Exploited Vulnerability

Date Added
2022-03-25
Patch Due Date
2022-04-15
Ransomware Use
Unknown
Required Action
Apply updates per vendor instructions.

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2020-03-04
Last Modified
2026-10-08
NVD status
Analyzed
GitHub Advisory
GHSA-w6h5-rjp3-hxvc

Frequently asked questions

What is CVE-2020-9054?

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

Is CVE-2020-9054 actively exploited?

Yes. CVE-2020-9054 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2022-04-15.

What is the CVSS score for CVE-2020-9054?

CVE-2020-9054 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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