How severe is CVE-2023-33009?

CVE-2023-33009 has a CVSS 3.1 base score of 9.8 (CRITICAL). EPSS estimates a 28.1% probability of exploitation in the next 30 days. It is listed in the CISA Known Exploited Vulnerabilities catalog.

CVE-2023-33009: Zyxel Multiple Firewalls Buffer Overflow

CISA Known Exploited Vulnerabilities

Zyxel Multiple Firewalls Buffer Overflow Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Added to KEV

2023-06-05

Remediation due

2023-06-26

Required action
Apply updates per vendor instructions.

CISA notes
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewalls; https://nvd.nist.gov/vuln/detail/CVE-2023-33009

Description

A buffer overflow vulnerability in the notification function in Zyxel ATP series firmware versions 4.60 through 5.36 Patch 1, USG FLEX series firmware versions 4.60 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.60 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.60 through 5.36 Patch 1, VPN series firmware versions 4.60 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.60 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.

Severity

CVSS 3.1 · CNA9.8 CRITICAL

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

SSVC · CISA-ADP

Exploitationactive

Automatableyes

Technical impacttotal

Affected Products

Vendor	Product	Affected versions
Zyxel	ATP series firmware	4.60 through 5.36 Patch 1
Zyxel	USG FLEX series firmware	4.60 through 5.36 Patch 1
Zyxel	USG FLEX 50(W) firmware	4.60 through 5.36 Patch 1
Zyxel	USG20(W)-VPN firmware	4.60 through 5.36 Patch 1
Zyxel	VPN series firmware	4.60 through 5.36 Patch 1
Zyxel	ZyWALL/USG series firmware	4.60 through 4.73 Patch 1

References

1 Links

Other references

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewalls

Record Details

Published

2023-05-24

Last updated

2025-10-21

Assigner (CNA)

Zyxel

Credited to

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Related Tool Categories

Tool categories that test for or protect against this vulnerability class.

CWE-120 · Buffer Overflow

Fuzzing Binary Exploitation

CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.