Evidence dossier

CVE-2023-33009

CVE-2023-33009

75.1–90.1Priority evidence range

As known Jul 19, 2026, 5:00 AM UTCgen-56ccdaf9

Normalized restatement

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.

State: PUBLISHED
Published: May 24, 2023
Updated: Oct 21, 2025
Evidence coverage: 85%

CISA KEVCatalog member

Apply updates per vendor instructions.

FIRST EPSS28.14%

2026-07-18 · v2026.06.15 · percentile 97.9%

Source stateNo scored conflict

Distinct CVSS assessments remain side by side; none are averaged.

Source comparison

Who said what

CISA-ADPindependent enrichment

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CISA ADP Vulnrichment

Jul 19, 2026Original evidence ↗

CVEderivative copy

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CVE Program Container

Jul 19, 2026Original evidence ↗

Zyxeloriginal assertion

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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.

Jul 19, 2026Original evidence ↗

CISA KEVoriginal assertion

observed_exploitation

Zyxel Multiple Firewalls Buffer Overflow Vulnerability

Jul 19, 2026Original evidence ↗

FIRST EPSSoriginal assertion

model_probability

Probability 0.281440000000; percentile 0.978910000000

Jul 19, 2026Original evidence ↗

Applicability

Cited product scope

Trace impact →

ZyxelATP series firmware

[{"status": "affected", "version": "4.60 through 5.36 Patch 1"}]unknown

ZyxelUSG20(W)-VPN firmware

[{"status": "affected", "version": "4.60 through 5.36 Patch 1"}]unknown

ZyxelUSG FLEX 50(W) firmware

[{"status": "affected", "version": "4.60 through 5.36 Patch 1"}]unknown

ZyxelUSG FLEX series firmware

[{"status": "affected", "version": "4.60 through 5.36 Patch 1"}]unknown

ZyxelVPN series firmware

[{"status": "affected", "version": "4.60 through 5.36 Patch 1"}]unknown

ZyxelZyWALL/USG series firmware

[{"status": "affected", "version": "4.60 through 4.73 Patch 1"}]unknown

Unknown vendorUnknown product

cpe:2.3:h:zyxel:atp100:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:atp100w:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:atp200:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:atp500:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:atp700:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:atp800:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg20-vpn:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_20w-vpn:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_40:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_40w:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_60:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_60w:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_100:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_100w:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_200:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_50:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_500:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_50w:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:usg_flex_700:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:vpn100:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:vpn1000:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:vpn300:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:h:zyxel:vpn50:-:*:*:*:*:*:*:*constrained

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp100_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp100_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp100_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp100w_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp100w_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp100w_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp200_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp200_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp200_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp500_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp500_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp500_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp700_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp700_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp700_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp800_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp800_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:atp800_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg20-vpn_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg20-vpn_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg20-vpn_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_20w-vpn_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_20w-vpn_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_20w-vpn_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_40_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 4.73supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_40_firmware:4.73:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_40_firmware:4.73:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_40w_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 4.73supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_40w_firmware:4.73:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_40w_firmware:4.73:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_60_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 4.73supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_60_firmware:4.73:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_60_firmware:4.73:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_60w_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 4.73supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_60w_firmware:4.73:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_60w_firmware:4.73:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_100_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_100_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_100_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_100w_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_100w_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_100w_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_200_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_200_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_200_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_500_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_500_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_500_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_50_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_50_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_50_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_50w_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_50w_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_50w_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_700_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_700_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:usg_flex_700_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn1000_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn1000_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn1000_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn100_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn100_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn100_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn300_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn300_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn300_firmware:5.36:patch1:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn50_firmware:*:*:*:*:*:*:*:*; start including 4.60; end excluding 5.36supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn50_firmware:5.36:-:*:*:*:*:*:*supported

Unknown vendorUnknown product

cpe:2.3:o:zyxel:vpn50_firmware:5.36:patch1:*:*:*:*:*:*supported

Assessments

CVSS by origin

9.8

nvd@nist.govCVSS 3.1 · role SecondaryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

9.8

security@zyxel.com.twCVSS 3.1 · role SecondaryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

9.8

ZyxelCVSS 3.1 · role unknownCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Limitations and unknowns

KEV membership is authoritative for the catalog, not proof of exposure in any environment.
EPSS is a dated model probability and not an individual-environment prediction.
Affected or fixed status applies only to the exact cited product and version scope; unresolved scope remains unknown.
NVD-carried upstream facts remain derivative and are not independent corroboration.
Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
Factor D is unknown in Public Core because no accepted canonical mapping-obligation ledger is present.
Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.