CVE-2020-9054: ZyXEL NAS products running firmware version 5.21 and earlier are vulnerable to pre-authentication command injection in weblogin.cgi

1. In CISA KEVCISA KEV catalogue25 Mar 2022
2. Exploited (reported): not seen
3. Scanning observed: not seen
4. Proof of concept public: not seen
5. Not established: not seen

DescriptionCVE.org

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

• ZyXEL · NAS326from V5.21(AAZF.7)C0 up to and including V5.21(AAZF.7)C0
• ZyXEL · NAS520from V5.21(AASZ.3)C0 up to and including V5.21(AASZ.3)C0
• ZyXEL · NAS540from V5.21(AATB.4)C0 up to and including V5.21(AATB.4)C0
• ZyXEL · NAS542from V5.21(ABAG.4)C0 up to and including V5.21(ABAG.4)C0
• ZyXEL · NSA210all
• ZyXEL · NSA220all
• ZyXEL · NSA220+all
• ZyXEL · NSA221all
• ZyXEL · NSA310from V4.75(AALH.2)C0 up to and including V4.75(AALH.2)C0
• ZyXEL · NSA320all
• ZyXEL · NSA320Sfrom V4.75(AANV.2)C0 up to and including V4.75(AANV.2)C0
• ZyXEL · NSA325from V4.81(AAAJ.1)C0 up to and including V4.81(AAAJ.1)C0
• ZyXEL · NSA325v2from V4.81(AALS.1)C0 up to and including V4.81(AALS.1)C0

Exploitation

Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalogue.

CISA KEV

Listed since 25 Mar 2022 · catalogue entry

Public check

Zyxel NAS Firmware 5.21- Remote Code Execution · nuclei template in projectdiscovery/nuclei-templates

Weakness

OS Command Injection · Command and Code Injection

Vendor

ZyXEL

Published

March 2020

Band

Exploited in the wild, March 2020

1. 25 Mar 2022
   CISA added it to the KEV catalogue CISA

• NVD entrynvd.nist.gov
• CISA KEV cataloguecisa.gov
• CVE recordcve.org
• Weakness CWE-78cwe.mitre.org
• zyxel.com/support/remote-code-execution-vulnerability-of-NAS-prozyxel.com
• Third-party advisorykb.cert.org
• kb.cert.org/artifacts/cve-2020-9054.htmlkb.cert.org
• krebsonsecurity.com/2020/02/zyxel-fixes-0day-in-network-storage-krebsonsecurity.com