CVE-2023-33009
CRITICALCISA KEVEPSS 98th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 98% of all known CVEs.
Zyxel Multiple Firewalls Buffer Overflow Vulnerability
Zyxel ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN, VPN, and ZyWALL/USG firewalls contain a buffer overflow vulnerability in the notification function that could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and remote code execution on an affected device.
Apply updates per vendor instructions.
Remediation due: 2023-06-26
References
Related Vulnerabilities
Other CWE-120 (Classic Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2014-0195 | Medium | 6.8 | 100% | - | Fix |
| CVE-2017-7269 | Critical | 9.8 | 100% | KEV | - |
| CVE-2019-11043 | High | 8.7 | 99% | KEV + Ransom | Fix |
| CVE-2011-4862 | High | 10.0 | 95% | - | Fix |
| CVE-2007-5659 | High | 7.8 | 94% | KEV | Fix |
| CVE-2022-3786 | High | 7.5 | 92% | - | Fix |
Common questions
How do I fix CVE-2023-33009?
Published advisories record a fix for 23 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2023-33009 being actively exploited?
Yes. CVE-2023-33009 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2023-06-26. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2023-33009?
CVE-2023-33009 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2023-33009 affect?
Published advisories record a fix for atp100 firmware (NVD), atp100w firmware (NVD), atp200 firmware (NVD), atp500 firmware (NVD), and 19 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-02-26.