CVEs / CVE-2023-33009
CVE-2023-33009: Zyxel Multiple Firewalls Buffer Overflow Vulnerability
- Known exploited in the CISA KEV catalog since 5 Jun 2023
- critical 9.8 CVSS 3.1 (from the CNA)
- EPSS 28.1% chance of exploitation in the next 30 days, higher than 98% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| 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 | — |
Exploitation
| In CISA KEV since | 5 Jun 2023 |
|---|---|
| Due date for US federal agencies | 26 Jun 2023 |
| Used in ransomware campaigns | Unknown |
| Required action | Apply updates per vendor instructions. |
Severity
| CVSS 3.1 | 9.8 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-120 |
References
- CVE-2023-33009 on NVD
- CVE-2023-33009 in the CISA KEV catalog
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewalls (cited by CISA)
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewalls Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-33009 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.