Zyxel NAS - RCE (CVE-2020-9054)
89Exploiting IPs reported
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.
CrowdSec analysis
CVE-2020-9054 is a critical vulnerability in Zyxel network-attached storage (NAS) devices that allows remote, unauthenticated command injection through improper input sanitation in the login interface.
CrowdSec has been tracking this vulnerability and its exploits since 10th of March 2025.
Data from the CrowdSec community indicates that exploitation of CVE-2020-9054 is highly selective and intelligence-driven. Threat actors use advanced reconnaissance and carefully choose their targets, often as part of sophisticated campaigns or advanced persistent threat operations. Data from the CrowdSec community also indicates a gradual decrease in attacks targeting CVE-2020-9054. While still present in the wild, exploitation levels have dropped noticeably week-over-week. This may signal that the vulnerability is becoming less relevant or that defenses are improving fast enough for attackers to lose interest.
Exploitation attempts are identified by requests to URLs referencing cgi-bin/weblogin.cgi with crafted parameters designed to trigger command injection.
Exploitation
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Common Weakness Enumeration (CWE)
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Blocklist
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