high
8.8
CWE
78 77
Advisory Published
Updated

CVE-2023-27991: OS Command Injection

First published: Mon Apr 24 2023(Updated: )

The post-authentication command injection vulnerability in the CLI command of Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.16 through 5.35, USG20(W)-VPN firmware versions 4.16 through 5.35, and VPN series firmware versions 4.30 through 5.35, which could allow an authenticated attacker to execute some OS commands remotely.

Credit: security@zyxel.com.tw

Affected SoftwareAffected VersionHow to fix
Zyxel ATP200 firmware>=4.32<5.36
Zyxel ATP200 firmware
Zyxel ZyWall ATP100 Firmware>=4.32<5.36
Zyxel ATP100 Firmware
Zyxel Zywall ATP700 Firmware>=4.32<5.36
Zyxel ATP700 Firmware
Zyxel ATP500 Firmware>=4.32<5.36
Zyxel ATP500 Firmware
Zyxel ATP100W Firmware>=4.32<5.36
Zyxel ATP100W Firmware
Zyxel ATP800>=4.32<5.36
Zyxel ATP800 Firmware
Zyxel USG Flex 100 firmware>=4.50<5.36
Zyxel USG FLEX 100
Zyxel USG FLEX 50(W) series firmware>=4.50<5.36
Zyxel USG FLEX 50
Zyxel USG FLEX 200>=4.50<5.36
Zyxel USG FLEX 200 firmware
Zyxel USG FLEX 500>=4.50<5.36
Zyxel USG FLEX 500 firmware
Zyxel USG FLEX firmware>=4.50<5.36
Zyxel USG FLEX 700 firmware
Zyxel USG FLEX 100w firmware>=4.50<5.36
Zyxel USG FLEX 100w firmware
Zyxel USG 20w-VPN Firmware>=4.16<5.36
Zyxel USG20
Zyxel USG FLEX 50w>=4.16<5.36
Zyxel USG FLEX 50(W) series firmware
Zyxel USG20-VPN>=4.30<5.36
Zyxel USG20
Zyxel VPN100>=4.30<5.36
Zyxel VPN100 Firmware
Zyxel VPN1000 Firmware>=4.30<5.36
Zyxel VPN1000 Firmware
Zyxel Zywall VPN 300 Firmware>=4.30<5.36
Zyxel Zywall VPN300
Zyxel Zywall VPN 50 Firmware>=4.30<5.36
Zyxel VPN50 Firmware

Never miss a vulnerability like this again

Sign up to SecAlerts for real-time vulnerability data matched to your software, aggregated from hundreds of sources.

Read MoreStart Free Trial

Reference Links

Frequently Asked Questions

  • What is CVE-2023-27991?

    CVE-2023-27991 is a post-authentication command injection vulnerability in the CLI command of Zyxel ATP series firmware versions 4.32 through 5.35.

  • Which Zyxel products are affected by CVE-2023-27991?

    Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.16 through 5.35, USG20(W)-VPN firmware versions 4.16 through 5.35, and VPN series.

  • What is the severity of CVE-2023-27991?

    CVE-2023-27991 has a severity value of 8.8 (high).

  • How can I fix CVE-2023-27991?

    To fix CVE-2023-27991, you should update the affected firmware versions to 5.36 for ATP series and USG FLEX series, and to 4.30 for USG20(W)-VPN and VPN series.

  • Where can I find more information about CVE-2023-27991?

    You can find more information about CVE-2023-27991 at the following link: [Zyxel Security Advisory](https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-xss-vulnerability-and-post-authentication-command-injection-vulnerability-in-firewalls)

Company

Resources

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2025 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203