CVE Intelligence
Medium Access control

CVE-2026-12489 — Incorrect Authorization in Zyxel Ex3501-t0 Firmware

An incorrect authorization vulnerability in the Data Access Layer (DAL) of Zyxel EX3501-T0 firmware versions through 5.44(ACHR.6)C0 could allow an authenticated attacker to escalate privileges by modifying the login_privilege data on an affected device.

Published Oct 20, 2026 · Updated Oct 20, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Zyxel

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
  • Technical severity (medium)+3

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
—
No EPSS score.
Affects
Zyxel
Ex3501-t0 Firmware
CVSS base
6.5
Medium · 2 source(s)

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.

  1. Identify exposed assets running the affected vendor/product/version combinations (Zyxel Ex3501-t0 Firmware).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. 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.

VendorProductVersionsStatusSource
Zyxel Ex3501-t0 Firmware version <= 5.44(ACHR.6)C0 Vulnerable CVE Program (cve.org) e CISA ADP

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
None
Availability
None

Every base score collected

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

ScoreVersionSeverityExpl.ImpactScored by
6.5 CVSS 3.1 Medium 2.8 3.6 security@zyxel.com.tw via NIST National Vulnerability Database
6.5 CVSS 3.1 Medium — — 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:N/A:N (score shown at the top: security@zyxel.com.tw)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-863 · Incorrect Authorization

Other CVEs with this weakness →

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/ex3501-t0 firmware
    Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 20, 2026
  • CVSS changed · 6.5
    Oct 20, 2026 · NIST National Vulnerability Database
  • Source status changed · → Received
    Oct 20, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 20, 2026 · Alertas do Telegram
  • CVE published
    Oct 20, 2026 · Zyxel

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 20, 2026 – Oct 20, 2026
  • 1× Official description updated · Oct 20, 2026 – Oct 20, 2026

References

1 on the record

Elsewhere on this site

Zyxel
every CVE for this vendor
Access control
same class
CWE-863
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-0711 OS Command Injection in Zyxel Nr5307 Firmware Apr 28, 2026
  • CVE-2026-1460 OS Command Injection in Zyxel Nebula Fwa70 Firmware Apr 28, 2026
  • CVE-2025-11848 NULL Pointer Dereference in Zyxel Ex5601-t1 Firmware Feb 24, 2026
  • CVE-2025-13943 OS Command Injection in Zyxel Ex5601-t1 Firmware Feb 24, 2026
  • CVE-2025-11847 NULL Pointer Dereference in Zyxel Ex3510-b1 Firmware Feb 24, 2026
  • CVE-2025-11846 NULL Pointer Dereference in Zyxel Lte3301-plus Firmware Feb 23, 2026

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 FIRST EPSS score.
  • No fixed version, patch or mitigation documented.
  • No CISA SSVC assessment.
  • 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-2026-12489 is "Incorrect Authorization in Zyxel Ex3501-t0 Firmware", rated Medium. It affects Ex3501-t0 Firmware (Zyxel); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. 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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