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CVE-2023-6764

HIGH

8.1

CVSS Score

Published: February 20, 2024 at 02:14 AM UTC

Updated: June 17, 2026 at 06:51 AM UTC

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

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Severity

HIGH8.1

Exploit prediction

EPSS 0.9%

SSVC

No known exploit

Description

A format string vulnerability in a function of the IPSec VPN feature 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, and USG20(W)-VPN series firmware versions from 4.16 through 5.37 Patch 1 could allow an attacker to achieve unauthorized remote code execution by sending a sequence of specially crafted payloads containing an invalid pointer; however, such an attack would require detailed knowledge of an affected device’s memory layout and configuration.

Affected

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

ATP100 Firmware · Zyxel

95%

4.32 ≤ 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%

4.32 ≤ 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%

4.32 ≤ 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%

4.32 ≤ 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%

4.32 ≤ 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%

4.32 ≤ 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)

Usg 20W VPN Firmware · Zyxel

95%

4.16 ≤ v ≤ 5.37patch14.16 ≤ v < 5.374.16 5.37 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%

4.50 ≤ 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%

4.50 ≤ 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-100ax (same device)

Usg Flex 100H Firmware · Zyxel

95%

4.50 ≤ 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-100h (same device)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-aps-02-20-2024

References (1)

Vendor Advisory

Source: [email protected]

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-aps-02-20-2024

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.1HIGHZyxel

Attack Vector: NETWORK
Complexity: HIGH
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: HIGH
Integrity: HIGH
Availability: HIGH

Vector?

Quick Info

StatusANALYZED

CWE

CWE-134

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