CVE-2020-9054
Zyxel Multiple NAS Devices OS Command Injection
- Published4 Mar 2020
- Added to CISA KEV25 Mar 2022
- Remediation due15 Apr 2022
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 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAffected products
Remediation
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.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-9054
- https://www.zyxel.com/support/remote-code-execution-vulnerability-of-NAS-products.shtml
Related CVEs
Recent high-severity vulnerabilities sharing a weakness type.
Frequently asked
Is CVE-2020-9054 being actively exploited?
Yes. CVE-2020-9054 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 25 Mar 2022.
How severe is CVE-2020-9054?
CVE-2020-9054 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 100.0% probability of exploitation.
Which products are affected by CVE-2020-9054?
Affected products include Zyxel Atp100 Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp800 Firmware, Zyxel Nas326 Firmware, and 19 more.
How do I fix CVE-2020-9054?
Upgrade affected software to a fixed version, for example Zyxel Atp100 Firmware 4.35\(abps.3\)c0, Zyxel Atp200 Firmware 4.35\(abfw.3\)c0, Zyxel Atp500 Firmware 4.35\(abfu.3\)c0 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2020-9054 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.