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CVE-2023-33009

Buffer Copy without Checking Size of Input

CVSS 3.1 Critical 9.8Known exploited (CISA KEV)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

Official description from the CVE record, published by Zyxel. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org

Key data

CVSS 3.1 Critical 9.8

Score published by Zyxel in the CVE record.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Network

    The vulnerable component can be reached over a network, possibly from the Internet.

  • Attack complexity: Low

    No special conditions are needed. The attack can be repeated at will.

  • Privileges required: None

    No account or privileges are needed.

  • User interaction: None

    No action from any user is needed.

  • Scope: Unchanged

    The impact stays within the vulnerable component.

  • Confidentiality impact: High

    Serious or total effect on the secrecy of data.

  • Integrity impact: High

    Serious or total effect on the trustworthiness of data.

  • Availability impact: High

    Serious or total effect on availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.
Score
0.28144 (28.1% probability)
Percentile
98.1%
Scores of
Nov 10, 2026
Model
v2026.06.15

CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.
Name in the catalog
Zyxel Multiple Firewalls Buffer Overflow Vulnerability
Added to the catalog
Jun 5, 2023
Federal due date
Jun 26, 2023

CISA assessment as of Feb 4, 2025

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.
Exploitation
Recorded by CISA as active
Automatable
yes
Technical impact
total

Weakness (CWE)

CWE catalog version 5.0.
CWE names: Copyright © 2006-2026, The MITRE Corporation. See /security/cve/legal for the CWE license.
  • CWE-120Buffer Copy without Checking Size of Input

Affected products

Products listed in the CVE record, as the CNA published them.

  • Zyxel ATP series firmware

    • affected: 4.60 through 5.36 Patch 1

  • Zyxel USG FLEX series firmware

    • affected: 4.60 through 5.36 Patch 1

  • Zyxel USG FLEX 50(W) firmware

    • affected: 4.60 through 5.36 Patch 1

  • Zyxel USG20(W)-VPN firmware

    • affected: 4.60 through 5.36 Patch 1

  • Zyxel VPN series firmware

    • affected: 4.60 through 5.36 Patch 1

  • Zyxel ZyWALL/USG series firmware

    • affected: 4.60 through 4.73 Patch 1

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Timeline

  1. ID reserved
  2. Record published
  3. Added to CISA KEV
  4. Record last updated

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About CubePath

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:25 UTC. Sources and licenses