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High

Missing authorization in Zyxel ZLD 2FA flow allows configuration download

IdentifiersCVE-2025-9133CWE-862· Missing Authorization

CVE-2025-9133 is a missing authorization vulnerability in Zyxel ZLD firmware affecting the web management authentication flow on Zyxel ATP, USG FLEX, USG FLEX 50(W), and USG20(W)-VPN devices. According to the provided content, after a user successfully completes only the first factor of two-factor authentication (username and password), the device creates a session object. Due to improper authorization logic, that pre-2FA-completion session is not adequately restricted and can be used to access sensitive resources before the second factor is verified. As a result, a semi-authenticated attacker can view and download the full system configuration from affected devices. Affected versions are ATP series V4.32 through V5.40, USG FLEX series V4.50 through V5.40, USG FLEX 50(W) series V4.16 through V5.40, and USG20(W)-VPN series V4.16 through V5.40. The issue affects devices in on-premise management mode; Nebula-managed devices are not affected.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an attacker with valid first-factor credentials, but without completing the second authentication factor, to access and download the device configuration. The exposed configuration may include sensitive security and operational data such as network topology, VPN settings, and user-related information. This undermines the protection expected from MFA/2FA and can materially aid follow-on compromise, including credential harvesting from stored configuration data, reconnaissance of internal network structure, and targeting of remote-access infrastructure.

Mitigation

If you can’t patch tonight, do this now.

Until patched, restrict access to the web management interface and any related management endpoints to trusted administrative networks only, preferably via VPN or dedicated management segments. Disable external exposure of administrative interfaces where possible. Monitor for anomalous login sessions that complete only first-factor authentication and review access to configuration export/download functions. Rotate credentials and secrets that may have been exposed in downloaded configurations, including VPN credentials, administrative passwords, certificates, and other embedded sensitive settings. Nebula-managed devices are stated to be unaffected.

Remediation

Patch, then assume compromise.

Apply Zyxel firmware updates that address CVE-2025-9133 for affected ZLD-based firewall products. Upgrade affected ATP, USG FLEX, USG FLEX 50(W), and USG20(W)-VPN devices from the vulnerable version ranges to a vendor-fixed release identified in Zyxel’s security advisory. For environments using on-premise management, prioritize patching internet-reachable management interfaces and any devices exposed to untrusted networks.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Zyxel CommunicationsZldoperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

15 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

15 SOURCESView more in app
What this page doesn’t show

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures1

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity13

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2025-9133
NVD
nvd.nist.gov/vuln/detail/CVE-2025-9133
MITRE CWE · CWE-862
Missing Authorization
Vendor Advisory
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