CVE-2023-28771
Zyxel Multiple Firewalls OS Command Injection Vulnerability
IN CISA KEV
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.
- Vendor
- Zyxel
- Product
- Multiple Firewalls
- CVSS 3.1
- 9.8 (critical), scored by security@zyxel.com.twCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CVSS 3.1
- 9.8 (critical), scored by NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CWE
- CWE-78
- Published
- 2023-04-25
- NVD modified
- 2026-06-17
- NVD status
- Analyzed
CISA KEV
- Date added
- 2023-05-31
- Due date
- 2023-06-21
- Ransomware use
- Unknown
- Required action
- Apply updates per vendor instructions.
EPSS
99.3% chance of exploitation in the next 30 days (percentile 99th)
FIRST EPSS, updated 17 Oct 2026. About EPSS
CVSS is severity, EPSS is likelihood, KEV means already exploited. EPSS is a statistical probability, not a certainty: a low score does not make a bug safe, and a high one does not prove it is being exploited.
References
- www.zyxel.com (Vendor Advisory)
- www.zyxel.com (Vendor Advisory)
- www.cisa.gov (US Government Resource)
Data last updated 18 Oct 2026. Sources: NVD API 2.0, CISA KEV catalog, FIRST EPSS. Links: NVD, CISA KEV. Metadata only. ThreatWire does not host exploit code.