Is CVE-2023-28771 in the CISA KEV catalog?

Yes. CVE-2023-28771 is on the CISA Known Exploited Vulnerabilities list, added 2023-05-31.

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

CVE-2023-28771 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2023-28771?

CVE-2023-28771 has an EPSS score of 99.28% (100th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2023-28771

CRITICALCISA KEVEPSS 100th pctl

9.8

CVSS v3

NVD

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.

CWE-78OS Command Injection

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

99.28%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Zyxel Multiple Firewalls OS Command Injection Vulnerability

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.

Apply updates per vendor instructions.

Remediation due: 2023-06-21

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-27.