High Access control

CVE-2025-9133 — Missing Authorization in Zyxel ATP series firmware

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.

Published Oct 21, 2025 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Zyxel

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 5.5% (30-day exploitation probability)+14
Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

5.46%

ahead of 93% of scored CVEs · Oct 14, 2026

Affects

Zyxel

ATP series firmware and 4 more

CVSS base

8.1

High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Zyxel ATP series firmware, Zyxel USG FLEX 50(W) series firmware, Zyxel USG FLEX series firmware…).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
EPSS ahead of 93% of scored CVEs: prioritize it in the patch queue.
Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Zyxel	ATP series firmware	version versions from V4.32 through V5.40	Vulnerable	CVE Program (cve.org) e CISA ADP
Zyxel	USG FLEX 50(W) series firmware	version versions from V4.16 through V5.40	Vulnerable	CVE Program (cve.org) e CISA ADP
Zyxel	USG FLEX series firmware	version versions from V4.50 through V5.40	Vulnerable	CVE Program (cve.org) e CISA ADP
Zyxel	USG20(W)-VPN series firmware	version versions from V4.16 through V5.40	Vulnerable	CVE Program (cve.org) e CISA ADP
Zyxel	Zld	≥ 4.32 and < 5.41≥ 4.50 and < 5.41≥ 4.16 and < 5.41	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
8.1	CVSS 3.1	High	2.8	5.2	security@zyxel.com.tw via NIST National Vulnerability Database
8.1	CVSS 3.1	High	—	—	Zyxel via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N (score shown at the top: security@zyxel.com.tw)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-862 · Missing Authorization

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 5.46%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Audit administrative actions and access to resources outside each user’s normal pattern.

web/proxy/WAF logsnetwork IDS/IPSauthentication logsapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · zyxel/atp series firmware, zyxel/usg flex series firmware, zyxel/usg flex 50(w) series firmware, zyxel/usg20(w)-vpn seri
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 8.1
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
2025
CVE published
Oct 21, 2025 · Zyxel

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-pos
Vendor Advisory, vendor-advisory, NIST National Vulnerability Database

Elsewhere on this site

Zyxel
every CVE for this vendor

Access control
same class

CWE-862
other pages naming this weakness

Related CVEs (same products)

High CVE-2025-11730 OS Command Injection in Zyxel ATP series firmware Feb 4, 2026
High CVE-2025-8078 OS Command Injection in Zyxel Zld Oct 21, 2025
Critical CVE-2024-11667 Zyxel Multiple Firewalls Path Traversal Vulnerability KEV Nov 27, 2024
Critical CVE-2023-33009 Zyxel Multiple Firewalls Buffer Overflow Vulnerability KEV May 24, 2023
Critical CVE-2023-33010 Zyxel Multiple Firewalls Buffer Overflow Vulnerability KEV May 24, 2023
Critical CVE-2023-28771 Zyxel Multiple Firewalls OS Command Injection Vulnerability KEV Apr 24, 2023

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-9133 is "Missing Authorization in Zyxel ATP series firmware", rated High. It affects ATP series firmware (Zyxel); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.1 describes technical severity. EPSS 5.46% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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