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CVE-2020-9054

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

Basic Information

CVE State: PUBLISHED
Reserved Date: February 18, 2020
Published Date: March 04, 2020
Last Updated: February 07, 2025
Vendor: ZyXEL
Product: NAS326, NAS520, NAS540, NAS542, NSA210, NSA220, NSA220+, NSA221, NSA310, NSA320, NSA320S, NSA325, NSA325v2
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

CVSS Scores

CVSS v3.1

9.8 - CRITICAL

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

SSVC Information

Exploitation: active
Technical Impact: total

Exploit Status

Exploited in the Wild: Yes (added 2022-03-25 00:00:00 UTC) Source
Proof of Concept Available: Yes (added 2021-09-09 16:16:34 UTC) Source

References

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

Known Exploited Vulnerability Information

Source	Added Date
CISA	2022-03-25 00:00:00 UTC

Scanner Integrations

Scanner	URL	Date Detected
Nuclei	https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2020/CVE-2020-9054.yaml	2025-04-26 00:00:00 UTC

Potential Proof of Concepts

Warning: These PoCs have not been tested and could contain malware. Use at your own risk.

darrenmartyn/CVE-2020-9054

Type: github • Created: 2021-09-09 16:16:34 UTC • Stars: 2

CVE-2020-9054 PoC for Zyxel