What is the CVSS score of CVE-2023-28771?

CVE-2023-28771 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 99.3%.

Is there a public PoC exploit available for CVE-2023-28771?

Yes, a public proof-of-concept exploit is available for CVE-2023-28771. Prioritise patching immediately. EPSS: 99.3%.

Zywall Usg 100 Firmware CVE-2023-28771

CRITICAL

OS Command Injection (CWE-78)

2023-04-25 security@zyxel.com.tw

Command Injection Zyxel Zywall Usg 100 Firmware Atp200 Firmware Atp500 Firmware Atp800 Firmware Vpn50 Firmware Vpn100 Firmware Vpn300 Firmware Atp100 Firmware Vpn1000 Firmware Atp100W Firmware Atp700 Firmware Usg Flex 100 Firmware Usg Flex 100W Firmware Usg Flex 200 Firmware Usg Flex 500 Firmware Usg Flex 700 Firmware Usg Flex 50W Firmware Usg Flex 50 Firmware Zywall Usg 310 Firmware

9.8

CVSS 3.1 · Vendor: zyxel

Severity by source

Vendor (zyxel) PRIMARY

9.8 CRITICAL

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

Primary rating from Vendor (zyxel) · only source for this CVE.

CVSS VectorVendor: zyxel

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Jul 14, 2026 - 04:22 CISA

CVE Published

Apr 25, 2023 - 02:15 cve.org

CRITICAL 9.8

DescriptionCVE.org

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.

AnalysisAI

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,. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Technical ContextAI

This vulnerability is classified as OS Command Injection (CWE-78), which allows attackers to execute arbitrary operating system commands on the host. 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. Affected products include: Zyxel Atp100 Firmware, Zyxel Atp100W Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware. Version information: through 4.73.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Avoid passing user input to shell commands. Use language-specific APIs instead of shell execution. Apply strict input validation with allowlists.