How severe is CVE-2023-33009?

CVE-2023-33009 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2023-33009 being actively exploited?

Yes. CVE-2023-33009 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2023-06-05, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2023-33009?

CVE-2023-33009 primarily affects Zyxel Atp100 Firmware. In total, 69 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-33009?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2023-33009 have an EU (EUVD) identifier?

Yes. CVE-2023-33009 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2023-37198. It is also flagged as exploited in the EUVD (since 2023-06-05).

When was CVE-2023-33009 published?

CVE-2023-33009 was published on 2023-05-24 and last updated on 2026-06-17.

CVE-2023-33009

CVE-2023-33009 is a critical-severity vulnerability in Zyxel Atp100 Firmware with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2023-06-05). The underlying weakness is classified as CWE-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 28% (98th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2023-06-05)
EU (EUVD) id: EUVD-2023-37198
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2023-06-05)
Weakness: CWE-120
Affected product: Zyxel Atp100 Firmware
Published: 2023-05-24
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2023-33009?: 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 severe is CVE-2023-33009?: CVE-2023-33009 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2023-33009 being actively exploited?: Yes. CVE-2023-33009 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2023-06-05, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2023-33009?: CVE-2023-33009 primarily affects Zyxel Atp100 Firmware. In total, 69 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-33009?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2023-33009 have an EU (EUVD) identifier?: Yes. CVE-2023-33009 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2023-37198. It is also flagged as exploited in the EUVD (since 2023-06-05).
When was CVE-2023-33009 published?: CVE-2023-33009 was published on 2023-05-24 and last updated on 2026-06-17.

References

Affected products (69)

cpe:2.3:o:zyxel:atp100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp100_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp100_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp200_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp200_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp500_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp500_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp500_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp100w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp100w_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp100w_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp700_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp700_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp800_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp800_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp800_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_200_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_200_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_500_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_500_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_500_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_700_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_700_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100w_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100w_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50w_firmware:5.36:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50w_firmware:5.36:patch1:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_20w-vpn_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Zyxel Atp100 Firmware

CVE-2023-33010 — Critical (CVSS 9.8): A buffer overflow vulnerability in the ID processing function in Zyxel ATP series firmware versions 4.32 through 5.36…
CVE-2023-28771 — Critical (CVSS 9.8): Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware…
CVE-2022-30525 — Critical (CVSS 9.8): A OS command injection vulnerability in the CGI program of Zyxel USG FLEX 100(W) firmware versions 5.00 through 5.21…
CVE-2022-0342 — Critical (CVSS 9.8): An authentication bypass vulnerability in the CGI program of Zyxel USG/ZyWALL series firmware versions 4.20 through…
CVE-2020-29583 — Critical (CVSS 9.8): Firmware version 4.60 of Zyxel USG devices contains an undocumented account (zyfwp) with an unchangeable password. The…
CVE-2020-9054 — Critical (CVSS 9.8): Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21 contain a pre-authentication…

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