CRITICALCVSS v3.1 9.8Actively exploited · CISA KEV since 2023-05-31Vulnerability

CVE-2023-28771

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.

Properties

Euvd product
USG FLEX series firmware, VPN series Firmware, ATP series firmware, ZyWALL/USG series firmware
Vulnerability name
Zyxel Multiple Firewalls OS Command Injection Vulnerability
First seen
2025-10-21T23:05:48+00:00
Cvss score
9.8
Epss score
0.99284
Last seen
2026-10-19T12:00:27+00:00
Due date
2023-06-21
Euvd assigner
Zyxel
Retrieved at
2026-10-21T01:24:47+00:00
Exploited euvd since
2023-05-31T00:00:00+00:00
Src batch id
epss_history-20261020T103617Z-728ddd
Source url
https://epss.empiricalsecurity.com/epss_scores-2026-10-19.csv.gz
Date added
2023-05-31
Score
9.8
Euvd base score version
3.1
Fetched at
2026-10-20T10:36:20+00:00
Euvd vendor
Zyxel
Cvss vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
In Signal since
initial import (Sep 2026)
Euvd base score
9.8

Related Entities (43 · showing 23)

AFFECTS_PRODUCT (40 · showing 20)

→[Product]cpe:2.3:o:zyxel:vpn1000_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:zywall_usg_310_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:vpn100_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:zywall_usg_100:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:vpn50_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:vpn300_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:zywall_usg_100_firmware:4.73:-:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:zywall_usg_310_firmware:4.73:-:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:zywall_usg_100_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:vpn300:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:vpn1000:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:vpn50:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:zywall_usg_310:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:vpn100:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:usg_flex_500:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:atp500_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:atp800:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:h:zyxel:atp100w:-:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:usg_flex_50w_firmware:*:*:*:*:*:*:*:*
→[Product]cpe:2.3:o:zyxel:usg_flex_700_firmware:*:*:*:*:*:*:*:*

DESCRIBES (1)

←[KEVEntry]Zyxel Multiple Firewalls OS Command Injection Vulnerability

HAS_WEAKNESS (1)

→[Weakness]Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

INVOLVES (1)

←[Signal]kev_added · 2023-05-31

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CVE-2023-28771 (CVSS v3.1 9.8) — Ninja Signal Threat Intelligence | Ninja Signal