How severe is CVE-2020-9054?

CVE-2020-9054 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which products are affected by CVE-2020-9054?

Affected package information for CVE-2020-9054 is not yet fully mapped. Check the official advisory links for details.

How do I patch CVE-2020-9054?

Apply the zyxel atp100 firmware security patch or hotfix for CVE-2020-9054 on the affected version, following the vendor advisory for your exact build.

How do I detect CVE-2020-9054 across my infrastructure?

Inventory every zyxel atp100 firmware deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

How do I mitigate CVE-2020-9054 if there is no patch (or I can't update yet)?

Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

How does O3 Security protect against CVE-2020-9054?

O3 detects and blocks CVE-2020-9054 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Is CVE-2020-9054 actively exploited in the wild?

Yes. There are 5 known exploit references for CVE-2020-9054, including 4 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

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

CVE-2020-9054 has an EPSS (Exploit Prediction Scoring System) score of 100.0%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2020-9054 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2020-9054 (Zyxel Multiple NAS Devices OS Command Injection Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-03-25. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-04-15. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2020-9054?

CVE-2020-9054 is classified as OS Command Injection (CWE-78). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2020-9054?

CVE-2020-9054 affects zyxel atp100 firmware; zyxel atp200 firmware; zyxel atp500 firmware; zyxel atp800 firmware, and 23 more product(s). Check the affected-products list on this page against your deployed version to confirm exposure.

Is there exploit tooling available for CVE-2020-9054?

A Nuclei detection template exists for CVE-2020-9054, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2020-9054 published, and has it been updated?

CVE-2020-9054 was published on March 4, 2020 and was last updated on June 17, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2022-03-25 — agencies required to remediate by 2022-04-15

CVE-2020-9054

CRITICAL

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…

Published

Mar 4, 2020

Updated

Jun 17, 2026

Affected

0 pkgs

Patched

None yet

Exploits

5 known

EPSS Exploitation Probability

via FIRST.org ↗

100.0%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

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

Affected Products

27 products · 27 configurations

atp100 firmwarezyxel

≥ 4.35 && < 4.35\(abps.3\)c0

range

atp200 firmwarezyxel

≥ 4.35 && < 4.35\(abfw.3\)c0

range

atp500 firmwarezyxel

≥ 4.35 && < 4.35\(abfu.3\)c0

range

atp800 firmwarezyxel

≥ 4.35 && < 4.35\(abiq.3\)c0

range

nas326 firmwarezyxel

< 5.21\(aazf.7\)c0

range

nas520 firmwarezyxel

< 5.21\(aasz.3\)c0

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Multiple ZyXEL network-attached storage (NAS) devices running firmware v…

krebsonsecurity.comNVDMar 2020

Multiple ZyXEL network-attached storage (NAS) devices running firmware v…

packetstormsecurity.comAPIFeb 2020

Multiple ZyXEL network-attached storage (NAS) devices running firmware v…

unit42.paloaltonetworks.comAPIMar 2020

Multiple ZyXEL network-attached storage (NAS) devices running firmware v…

cisa.govCISAMar 2022

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every zyxel atp100 firmware deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the zyxel atp100 firmware security patch or hotfix for CVE-2020-9054 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2020-9054 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Tailored to CVE-2020-9054. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

O3 Security · Runtime Protection

Is CVE-2020-9054 being exploited in your environment?

O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2020-9054 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.

Protect my workloads How runtime protection works

CVSS Score

9.8/10

CVSS v3 base score

Vector breakdown

AV:Attack Vector

Network

AC:Attack Complexity

Low

PR:Privileges Required

None

UI:User Interaction

None

S:Scope

Unchanged

C:Confidentiality

High

I:Integrity

High

A:Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE Classification

CWE-78OS Command Injection

Weaponization

Timeline

Disclosed

Mar 4, 2020

First exploit

Mar 6, 2020

2 days after disclosure — rapid exploitation

KEV added

Mar 25, 2022

Last updated

Jun 17, 2026

Identifiers

CVE-2020-9054

References

Advisorycwe.mitre.org Advisorykb.cert.org Advisorykb.cert.org Advisoryzyxel.com Advisorycwe.mitre.org Advisorykb.cert.org Advisorykb.cert.org Advisoryzyxel.com Exploit / PoCkrebsonsecurity.com Exploit / PoCkrebsonsecurity.com Webcisa.gov

Data from OSV.dev, enriched by O3 Security. Refreshed hourly.

CVE-2020-9054

EPSS Exploitation Probability

Description

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

Frequently Asked Questions

Is CVE-2020-9054 being exploited in your environment?