CVE-2023-6399

MEDIUM

6.5

CVSS Score

Published: February 20, 2024 at 01:42 AM UTC

Updated: June 17, 2026 at 06:50 AM UTC

47 products affected across 1 vendorUSG FLEX 200 firmwareUsg Flex 100W FirmwareUSG FLEX 700 firmware

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Severity

MEDIUM6.5

Exploit prediction

EPSS 0.6%

SSVC

No known exploit

Description

A format string vulnerability in Zyxel ATP series firmware versions from 4.32 through 5.37 Patch 1, USG FLEX series firmware versions from 4.50 through 5.37 Patch 1, USG FLEX 50(W) series firmware versions from 4.16 through 5.37 Patch 1, USG20(W)-VPN series firmware versions from 4.16 through 5.37 Patch 1, and USG FLEX H series firmware versions from 1.10 through 1.10 Patch 1 could allow an authenticated IPSec VPN user to cause DoS conditions against the “deviceid” daemon by sending a crafted hostname to an affected device if it has the “Device Insight” feature enabled.

Affected

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

ATP100 Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

ATP100W Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

zyxel-atp100w (same device)

ATP200 Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

zyxel-atp200 (same device)

ATP500 Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

zyxel-atp500 (same device)

ATP700 Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

zyxel-atp700 (same device)

ATP800 Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

zyxel-atp800 (same device)

Uos · Zyxel

95%

1.10 1.10 patch1

zyxel-usg-flex-100h (same device) · zyxel-usg-flex-100hp (same device) · zyxel-usg-flex-200h (same device) · zyxel-usg-flex-200hp (same device) · zyxel-usg-flex-500h (same device) · zyxel-usg-flex-700h (same device)

Usg 20W VPN Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

Usg Flex 100 Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1

Affected range stops below 5.37, so it looks safe — our inference, not a vendor statement

zyxel-usg-flex-100 (same device)

Usg Flex 100AX Firmware · Zyxel

95%

5.10 ≤ v < 5.375.37 5.37 patch1