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Vulnerabilities

Vulnerability · CVE-2023-28771

Zyxel Multiple Firewalls OS Command Injection Vulnerability

Published Apr 24, 2023 · catalog updated Jun 16, 2026 · Zyxel Multiple Firewalls

Patch now

CVE-2023-28771 is in the CISA known-exploited catalog, due Jun 21, 2023. Confirm Zyxel Multiple Firewalls against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
Critical9.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
99.28%
Remediation
Remediation guidance
Affected products
cpe zyxel/atp100 firmware · cpe zyxel/atp100w firmware · cpe zyxel/atp200 firmware · cpe zyxel/atp500 firmware · cpe zyxel/atp700 firmware · cpe zyxel/atp800 firmware

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe zyxel/atp100 firmwareversion unspecified
  • cpe zyxel/atp100w firmwareversion unspecified
  • cpe zyxel/atp200 firmwareversion unspecified
  • cpe zyxel/atp500 firmwareversion unspecified
  • cpe zyxel/atp700 firmwareversion unspecified
  • cpe zyxel/atp800 firmwareversion unspecified
  • cpe zyxel/usg flex 100 firmwareversion unspecified
  • cpe zyxel/usg flex 100w firmwareversion unspecified
  • cpe zyxel/usg flex 200 firmwareversion unspecified
  • cpe zyxel/usg flex 50 firmwareversion unspecified
  • cpe zyxel/usg flex 500 firmwareversion unspecified
  • cpe zyxel/usg flex 50w firmwareversion unspecified
  • vendor Zyxel Multiple Firewallsversion unspecified

How to fix CVE-2023-28771

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2023-28771 is in the CISA known-exploited catalog, due Jun 21, 2023. Confirm Zyxel Multiple Firewalls against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply updates per vendor instructions.

What should an analyst verify?

CWE-78: OS Command Injection. EPSS 99.28%. The CISA KEV listing is the exploitation evidence. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 24, 2023 · Catalog

    Detected

    Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

  2. May 31, 2023 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. Jun 21, 2023 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

Sources

  • CISA KEVConfirmed exploitationCVE-2023-28771

    Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firewalls allow for improper error message handling which could allow an unauthenticated attacker to execute OS commands remotely by sending crafted packets to an affected device.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2023-28771

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2023-28771

    30-day exploitation probability 99.3%

    first.org
  • Metasploit ModulesPublic exploit moduleexploit_linux/misc/zyxel_ike_decoder_rce_cve_2023_28771

    Public module reference (great). Module source is not copied into this catalog.

    rapid7.com
  • NIST NVDVulnerability recordCVE-2023-28771

    Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenti

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • VulnCheck KEVConfirmed exploitationCVE-2023-28771

    Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firewalls allow for improper error message handling which could allow an unauthenticated attacker to execute OS commands remotely by sending crafted packets to an affected device.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.