CVE-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…

Browse: All 2023 CVEs · All vendors

CVSS score: 9.8 Critical
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA KEV: Yes — actively exploited (added 2023-05-31, remediation due 2023-06-21)
Weakness (CWE): CWE-78
Published: 2023-04-25
Last modified: 2026-06-17
NVD status: Analyzed

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.

Affected products

zyxel atp100 firmware
zyxel atp100w firmware
zyxel atp200 firmware
zyxel atp500 firmware
zyxel atp700 firmware
zyxel atp800 firmware
zyxel usg flex 100 firmware
zyxel usg flex 100w firmware
zyxel usg flex 200 firmware
zyxel usg flex 50 firmware
zyxel usg flex 500 firmware
zyxel usg flex 50w firmware

Affected ranges per NVD CPE data; confirm exact versions in the vendor advisory.

Required action (CISA)

Apply updates per vendor instructions. Federal remediation deadline: 2023-06-21.

How to prioritize this

This vulnerability is on the CISA KEV list, meaning it is being actively exploited — treat it as urgent regardless of the raw CVSS number. Use the live CVE lookup for the latest NVD data, and the CVSS 3.1 calculator to model your own environmental score. For the actively exploited vulnerabilities that matter this week, read The Exploit HQ daily security brief.

References

FAQ

Is CVE-2023-28771 actively exploited?

Yes. CISA added CVE-2023-28771 to its Known Exploited Vulnerabilities (KEV) catalog on 2023-05-31, with a federal remediation deadline of 2023-06-21. A KEV listing means real-world exploitation is confirmed, so patching this should be prioritized above many higher-CVSS bugs that aren't being exploited.

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

CVE-2023-28771 has a CVSS base score of 9.8 (Critical). Its vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Related vulnerabilities

Data source: NVD & CISA KEV. Shown as-is; nothing added. Last generated from NVD data — re-check the live tool for updates.