CVE-2023-27991

Name: CVE-2023-27991
Creator: NVD / NIST
Published: 2023-04-24T18:15:09.497+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 1.51%

Last modified Jun 17, 2026

CVE-2023-27991 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. 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.. EPSS estimates a 1.51% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.51%

71.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Zyxel	Atp200 Firmware	>= 4.32, < 5.36
Zyxel	Atp100 Firmware	>= 4.32, < 5.36
Zyxel	Atp700 Firmware	>= 4.32, < 5.36
Zyxel	Atp500 Firmware	>= 4.32, < 5.36
Zyxel	Atp100w Firmware	>= 4.32, < 5.36
Zyxel	Atp800 Firmware	>= 4.32, < 5.36
Zyxel	Usg Flex 100 Firmware	>= 4.50, < 5.36
Zyxel	Usg Flex 50 Firmware	>= 4.50, < 5.36
Zyxel	Usg Flex 200 Firmware	>= 4.50, < 5.36
Zyxel	Usg Flex 500 Firmware	>= 4.50, < 5.36
Zyxel	Usg Flex 700 Firmware	>= 4.50, < 5.36
Zyxel	Usg Flex 100w Firmware	>= 4.50, < 5.36
Zyxel	Usg 20w-Vpn Firmware	>= 4.16, < 5.36
Zyxel	Usg Flex 50w Firmware	>= 4.16, < 5.36
Zyxel	Usg20-Vpn Firmware	>= 4.30, < 5.36
Zyxel	Vpn100 Firmware	>= 4.30, < 5.36
Zyxel	Vpn1000 Firmware	>= 4.30, < 5.36
Zyxel	Vpn300 Firmware	>= 4.30, < 5.36
Zyxel	Vpn50 Firmware	>= 4.30, < 5.36

References

Timeline

Published: Apr 24, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-27991?

How severe is CVE-2023-27991?

CVE-2023-27991 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.51% probability of exploitation in the next 30 days.

How do I fix CVE-2023-27991?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-27991?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST