CVE-2023-28771

Name: CVE-2023-28771
Creator: NVD / NIST
Published: 2023-04-25T02:15:08.743+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10Actively ExploitedEPSS 99.28%

Last modified Jun 17, 2026

CVE-2023-28771 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.. CISA has confirmed active exploitation in the wild. EPSS estimates a 99.28% chance of exploitation in the next 30 days.

Description

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

99.28%

99.9th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by Jun 21, 2023.

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Zyxel	Atp100 Firmware	>= 4.60, < 5.36
Zyxel	Atp100w Firmware	>= 4.60, < 5.35
Zyxel	Atp200 Firmware	>= 4.60, < 5.36
Zyxel	Atp500 Firmware	>= 4.60, < 5.36
Zyxel	Atp700 Firmware	>= 4.60, < 5.36
Zyxel	Atp800 Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 100 Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 100w Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 200 Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 50 Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 500 Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 50w Firmware	>= 4.60, < 5.36
Zyxel	Usg Flex 700 Firmware	>= 4.60, < 5.36
Zyxel	Vpn100 Firmware	>= 4.60, < 5.36
Zyxel	Vpn1000 Firmware	>= 4.60, < 5.36
Zyxel	Vpn300 Firmware	>= 4.60, < 5.36
Zyxel	Vpn50 Firmware	>= 4.60, < 5.36
Zyxel	Zywall Usg 310 Firmware	>= 4.60, < 4.73
Zyxel	Zywall Usg 310 Firmware	4.73
Zyxel	Zywall Usg 100 Firmware	>= 4.60, < 4.73
Zyxel	Zywall Usg 100 Firmware	4.73

References

http://packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.htmlExploit, Third Party Advisory
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewallsVendor Advisory
http://packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.htmlExploit, Third Party Advisory
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewallsVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28771US Government Resource

Timeline

Published: Apr 25, 2023
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2023-28771?

How severe is CVE-2023-28771?

CVE-2023-28771 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 99.28% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2023-28771?

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.

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Source: NVD / NIST