CVE-2023-33009A 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(…
Updated under an hour ago ()
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It affects Zyxel ATP series firmware and 28 other products. Add what you run to find out whether that includes you.
CISA lists it as known exploited since Jun 5, 2023; federal agencies had to remediate by Jun 26, 2023. Treat that date as your deadline.
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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.
- CVSS
- 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-120
- Known exploited
- Added to CISA KEV Jun 5, 2023; federal remediation due Jun 26, 2023Apply updates per vendor instructions.
- EPSS (exploitation in the next 30 days)
- 28.14% (percentile 98)
- Assigned by
- Zyxel
- NVD analysis
- Analyzed
- Record last updated
- Oct 21, 2025
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Zyxel ATP series firmware zyxel:atp_series_firmware (from the name) | 4.60 through 5.36 Patch 1 | CNA record |
Zyxel USG FLEX series firmware zyxel:usg_flex_series_firmware (from the name) | 4.60 through 5.36 Patch 1 | CNA record |
Zyxel USG FLEX 50(W) firmware zyxel:usg_flex_50_w_firmware (from the name) | 4.60 through 5.36 Patch 1 | CNA record |
Zyxel USG20(W)-VPN firmware zyxel:usg20_w_vpn_firmware (from the name) | 4.60 through 5.36 Patch 1 | CNA record |
Zyxel VPN series firmware zyxel:vpn_series_firmware (from the name) | 4.60 through 5.36 Patch 1 | CNA record |
Zyxel ZyWALL/USG series firmware zyxel:zywall_usg_series_firmware (from the name) | 4.60 through 4.73 Patch 1 | CNA record |
zyxel atp100_firmware zyxel:atp100_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel atp200_firmware zyxel:atp200_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel atp500_firmware zyxel:atp500_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel atp100w_firmware zyxel:atp100w_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel atp700_firmware zyxel:atp700_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel atp800_firmware zyxel:atp800_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_100_firmware zyxel:usg_flex_100_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_50_firmware zyxel:usg_flex_50_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_200_firmware zyxel:usg_flex_200_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_500_firmware zyxel:usg_flex_500_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_700_firmware zyxel:usg_flex_700_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_100w_firmware zyxel:usg_flex_100w_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_flex_50w_firmware zyxel:usg_flex_50w_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_20w-vpn_firmware zyxel:usg_20w-vpn_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel vpn100_firmware zyxel:vpn100_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel vpn50_firmware zyxel:vpn50_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel vpn300_firmware zyxel:vpn300_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel vpn1000_firmware zyxel:vpn1000_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg20-vpn_firmware zyxel:usg20-vpn_firmware | from 4.60 before 5.36; 5.36; 5.36 | NVD |
zyxel usg_40_firmware zyxel:usg_40_firmware | from 4.60 before 4.73; 4.73; 4.73 | NVD |
zyxel usg_40w_firmware zyxel:usg_40w_firmware | from 4.60 before 4.73; 4.73; 4.73 | NVD |
zyxel usg_60w_firmware zyxel:usg_60w_firmware | from 4.60 before 4.73; 4.73; 4.73 | NVD |
zyxel usg_60_firmware zyxel:usg_60_firmware | from 4.60 before 4.73; 4.73; 4.73 | NVD |
References
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewallsvendor-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-33009us-government-resource
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.