Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
CVE-2023-33009
Zyxel Multiple Firewalls
AV AC PR UI S C I A CVSS EPSS %ile KEV
N L N N U H H H 9.8 .2814 98.1 YES
AFFECTED
Product Versions Fixed
ATP series firmware 4.60 through 5.36 Patch 1 – —
USG FLEX series firmware 4.60 through 5.36 Patch 1 – —
USG FLEX 50(W) firmware 4.60 through 5.36 Patch 1 – —
USG20(W)-VPN firmware 4.60 through 5.36 Patch 1 – —
VPN series firmware 4.60 through 5.36 Patch 1 – —
ZyWALL/USG series firmware 4.60 through 4.73 Patch 1 – —
TIMELINE
May 17 Reserved by Zyxel
May 24 Published (CNA: Zyxel)
Jun 5 Added to CISA KEV, remediation due 2023-06-26
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.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| May 17, 2023 | Reserved | Reserved by Zyxel |
| May 24, 2023 | Published | Published (CNA: Zyxel) |
| June 5, 2023 | KEV ADDED | Added to CISA KEV, remediation due 2023-06-26 |
Affected
Affected products and packages — 6 rows
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| 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 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2023-33009 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.
