Zyxel NAS - RCE (CVE-2020-9054)
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.
psychologyCrowdSec 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 27th of February 2025.
Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2020-9054 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning. CrowdSec network telemetry also shows that exploitation of CVE-2020-9054 has significantly declined over the past week. Attack volumes are well below the long-term average, suggesting attackers are rapidly losing interest. The vulnerability appears to be falling out of active use across most threat landscapes.
Exploitation attempts are identified by requests to URLs referencing cgi-bin/weblogin.cgi with crafted parameters designed to trigger command injection.
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| Event | Date |
|---|---|
| CVE Published | 2020-04-03 |
| CISA KEV | 2022-03-25 |
| CISA Remediation Deadline | 2022-04-15 |
| Rule Released | 2025-02-27 |
| CrowdSec First Seen | 2025-02-27 |
Remediation & Protection
External References
- https://krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-devices/
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2020/CVE-2020-9054.yaml
- https://kb.cert.org/artifacts/cve-2020-9054.html
- https://kb.cert.org/vuls/id/498544/
- https://cwe.mitre.org/data/definitions/78.html