CVE-2023-4398

HIGH

7.5

CVSS Score

Published: November 28, 2023 at 01:48 AM UTC

Updated: June 17, 2026 at 06:37 AM UTC

28 products affected across 1 vendorZldUsg Flex 200Usg Flex 500

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Severity

HIGH7.5

Exploit prediction

EPSS 0.9%

SSVC

No known exploit

Description

An integer overflow vulnerability in the source code of the QuickSec IPSec toolkit used in the VPN feature of the Zyxel ATP series firmware versions 4.32 through 5.37, USG FLEX series firmware versions 4.50 through 5.37, USG FLEX 50(W) series firmware versions 4.16 through 5.37, USG20(W)-VPN series firmware versions 4.16 through 5.37, and VPN series firmware versions 4.30 through 5.37, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions on an affected device by sending a crafted IKE packet.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Zld · Zyxel

95%

4.16 ≤ v ≤ 5.374.30 ≤ v ≤ 5.374.32 ≤ v ≤ 5.374.50 ≤ v ≤ 5.37

zyxel-atp100 (environment) · zyxel-atp100w (environment) · zyxel-atp200 (environment) · zyxel-atp500 (environment) · zyxel-atp700 (environment) · zyxel-atp800 (environment) · zyxel-usg-20w-vpn (environment) · zyxel-usg-flex-100 (environment) · zyxel-usg-flex-100w (environment) · zyxel-usg-flex-200 (environment) · zyxel-usg-flex-50 (environment) · zyxel-usg-flex-500 (environment) · zyxel-usg-flex-50w (environment) · zyxel-usg-flex-700 (environment) · zyxel-vpn100 (environment) · zyxel-vpn1000 (environment) · zyxel-vpn300 (environment) · zyxel-vpn50 (environment) · zyxel-vpn50w (environment)

ATP · Zyxel

60%

v ≤ 5.374.32 ≤ v ≤ 5.374.32

Usg 20W VPN Firmware · Zyxel

60%

4.16 ≤ v ≤ 5.374.16

USG FLEX · Zyxel

60%

v ≤ 5.374.50 ≤ v ≤ 5.374.50

Usg Flex 50 · Zyxel

60%

v ≤ 5.37