CVE-2025-9133: zld Auth Bypass — Fix

Description

A missing authorization vulnerability in Zyxel ATP series firmware versions from V4.32 through V5.40, USG FLEX series firmware versions from V4.50 through V5.40, USG FLEX 50(W) series firmware versions from V4.16 through V5.40, and USG20(W)-VPN series firmware versions from V4.16 through V5.40 could allow a semi-authenticated attacker—who has completed only the first stage of the two-factor authentication (2FA) process—to view and download the system configuration from an affected device.

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CVSS v3.1 Score

8.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Weakness Type (CWE)

CWE-862 Missing Authorization

Affected Products

Vendor	Product	Versions
zyxel	zld	4.32 — 5.41
zyxel	atp100	All
zyxel	atp100w	All
zyxel	atp200	All
zyxel	atp500	All
zyxel	atp700	All
zyxel	atp800	All
zyxel	zld	4.50 — 5.41
zyxel	usg_flex_100	All
zyxel	usg_flex_100ax	All
zyxel	usg_flex_100w	All
zyxel	usg_flex_200	All
zyxel	usg_flex_50	All
zyxel	usg_flex_500	All
zyxel	usg_flex_50ax	All
zyxel	usg_flex_700	All
zyxel	zld	4.16 — 5.41
zyxel	usg_20w-vpn	All
zyxel	usg_flex_50w	All

References

Advisories & Patches

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-post-authentication-command-injection-and-missing-authorization-vulnerabilities-in-zld-firewalls-10-21-2025

Frequently Asked Questions

What is CVE-2025-9133? +

A missing authorization vulnerability in Zyxel ATP series firmware versions from V4.32 through V5.40, USG FLEX series firmware versions from V4.50 through V5.40, USG FLEX 50(W) series firmware versions from V4.16 through V5.40, and USG20(W)-VPN series firmware versions from V4.16 through V5.40 could allow a semi-authenticated attacker—who has completed only the first stage of the two-factor authentication (2FA) process—to view and download the system configuration from an affected device. It has a CVSS v3.1 base score of 8.1 (HIGH).

How severe is CVE-2025-9133? +

CVE-2025-9133 has a CVSS v3.1 score of 8.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-9133? +

CVE-2025-9133 affects products from zyxel, specifically: atp100, atp100w, atp200, atp500, atp700, atp800, usg_20w-vpn, usg_flex_100, usg_flex_100ax, usg_flex_100w, usg_flex_200, usg_flex_50, usg_flex_500, usg_flex_50ax, usg_flex_50w, usg_flex_700, zld. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-9133? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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