Answer in brief
CVE-2023-33009 records a High severity vulnerability in CVE Program Container. The current sources mark it as known exploited. The current feed maps Zyxel/ATP series firmware (generic), Zyxel/USG20(W)-VPN firmware (generic), Zyxel/USG FLEX 50(W) firmware (generic), Zyxel/USG FLEX series firmware (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. Known-exploitation status makes exposure review time-sensitive. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Zyxel/ATP series firmware (generic), Zyxel/USG20(W)-VPN firmware (generic), Zyxel/USG FLEX 50(W) firmware (generic), Zyxel/USG FLEX series firmware (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Zyxel/ATP series firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/USG20(W)-VPN firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/USG FLEX 50(W) firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/USG FLEX series firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/VPN series firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/ZyWALL/USG series firmwaregeneric | 4.60 through 4.73 Patch 1 | Not reported |
Published upstream
May 24, 2023
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 21, 2025
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
May 24, 2026
Added to CISA KEV
Jun 5, 2023
Evidence: source:kev:kev:kev:recordA 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.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2023-33009 records a High severity vulnerability in CVE Program Container. The current sources mark it as known exploited. The current feed maps Zyxel/ATP series firmware (generic), Zyxel/USG20(W)-VPN firmware (generic), Zyxel/USG FLEX 50(W) firmware (generic), Zyxel/USG FLEX series firmware (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. Known-exploitation status makes exposure review time-sensitive. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Zyxel/ATP series firmware (generic), Zyxel/USG20(W)-VPN firmware (generic), Zyxel/USG FLEX 50(W) firmware (generic), Zyxel/USG FLEX series firmware (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Zyxel/ATP series firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/USG20(W)-VPN firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/USG FLEX 50(W) firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/USG FLEX series firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/VPN series firmwaregeneric | 4.60 through 5.36 Patch 1 | Not reported |
| Zyxel/ZyWALL/USG series firmwaregeneric | 4.60 through 4.73 Patch 1 | Not reported |
Published upstream
May 24, 2023
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 21, 2025
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
May 24, 2026
Added to CISA KEV
Jun 5, 2023
Evidence: source:kev:kev:kev:recordA 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.
Quoted source text, attributed separately from HOL analysis.