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CVE-2023-28771

Zyxel Multiple Firewalls OS Command Injection

9.8 CRITICALActively exploited (CISA KEV)Public exploitEPSS 99.3%
  1. Published25 Apr 2023
  2. Added to CISA KEV31 May 2023
  3. Remediation due21 Jun 2023
Actively exploited (CISA KEV)

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.

Added to KEV: 31 May 2023Federal remediation due: 21 Jun 2023

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Zyxel Atp100 Firmware≥ 4.60 < 5.36
Zyxel Atp100w Firmware≥ 4.60 < 5.35
Zyxel Atp200 Firmware≥ 4.60 < 5.36
Zyxel Atp500 Firmware≥ 4.60 < 5.36
Zyxel Atp700 Firmware≥ 4.60 < 5.36
Zyxel Atp800 Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 100 Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 100w Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 200 Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 500 Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 50 Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 50w Firmware≥ 4.60 < 5.36
Zyxel Usg Flex 700 Firmware≥ 4.60 < 5.36
Zyxel Vpn1000 Firmware≥ 4.60 < 5.36
Zyxel Vpn100 Firmware≥ 4.60 < 5.36
Zyxel Vpn300 Firmware≥ 4.60 < 5.36
Zyxel Vpn50 Firmware≥ 4.60 < 5.36
Zyxel Zywall Usg 100 Firmware≥ 4.60 < 4.73 · 4.73
Zyxel Zywall Usg 310 Firmware≥ 4.60 < 4.73 · 4.73

Remediation

Fixed in
Zyxel Atp100 Firmware≥ 5.36
Zyxel Atp100w Firmware≥ 5.35
Zyxel Atp200 Firmware≥ 5.36
Zyxel Atp500 Firmware≥ 5.36
Zyxel Atp700 Firmware≥ 5.36
Zyxel Atp800 Firmware≥ 5.36
Zyxel Usg Flex 100 Firmware≥ 5.36
Zyxel Usg Flex 100w Firmware≥ 5.36
Zyxel Usg Flex 200 Firmware≥ 5.36
Zyxel Usg Flex 500 Firmware≥ 5.36

References

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Frequently asked

Is CVE-2023-28771 being actively exploited?

Yes. CVE-2023-28771 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 31 May 2023.

How severe is CVE-2023-28771?

CVE-2023-28771 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 99.3% probability of exploitation.

Which products are affected by CVE-2023-28771?

Affected products include Zyxel Atp100 Firmware, Zyxel Atp100w Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware, and 14 more.

How do I fix CVE-2023-28771?

Upgrade affected software to a fixed version, for example Zyxel Atp100 Firmware 5.36, Zyxel Atp100w Firmware 5.35, Zyxel Atp200 Firmware 5.36 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2023-28771 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.