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CVE-2020-9054 — Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21…

Key facts

CVE-2020-9054 is a Critical (9.8) vulnerability: Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2022-03-25), confirming active exploitation in the wild.

Actively exploited — on the CISA KEV catalog

CVE-2020-9054 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2022-03-25), confirming exploitation in the wild. Federal remediation deadline: 2022-04-15. Prioritise patching and deploy the detection and prevention rules below.
CVE CVE-2020-9054
Severity Critical (9.8)
CISA KEV Actively exploited (added 2022-03-25)
Detection / prevention —
PoC poc.py
Source 2020/CVE-2020-9054/

Details

English | 한국어

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

Vulnerability Details

Property Value
CVE ID CVE-2020-9054
Type RCE
CVSS Score 9.8

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2020/CVE-2020-9054/poc.py

Usage

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start

# Clone and navigate to CVE directory
cd CVE-2020-9054

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints

Application URL Status
Vulnerable App http://localhost:8080 Shows vulnerability
Patched App http://localhost:8081 Demonstrates fix

Directory Structure

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References

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

Generated by PoC Generator on 2026-07-01T21:58:11.402183385

Frequently asked questions

What is CVE-2020-9054?

CVE-2020-9054 is a Critical (9.8) vulnerability: Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2022-03-25), confirming active exploitation in the wild.

How do I detect CVE-2020-9054?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2020-9054?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

Is CVE-2020-9054 actively exploited?

Yes. CVE-2020-9054 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2022-03-25, which means it has been exploited in the wild. CISA set a federal remediation deadline of 2022-04-15. Prioritise patching and deploy the detection and prevention rules above.

For authorized security testing and research only. See the full source and NVD record.