What is the CVSS score of CVE-2023-35137?

CVE-2023-35137 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.9%.

Is there a patch available for CVE-2023-35137?

Yes, a patch is available for CVE-2023-35137. Update the affected software to the latest version immediately.

Nas326 Firmware CVE-2023-35137

HIGH

Improper Authentication (CWE-287)

2023-11-30 security@zyxel.com.tw

Authentication Bypass Zyxel Nas326 Firmware Nas542 Firmware

7.5

CVSS 3.1 · NVD

View

Vulnerability Assessment

Weakness	CWE CWE-287 OWASP Top 10:2025 A07:2025 - Authentication Failures ASVS 5.0 V6 - Authentication Authentication mechanism validation MITRE ATT&CK 2 techniques across 2 tactics: Defense Evasion, Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	A remote attacker could bypass authentication mechanisms to gain unauthorized access by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.9% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAI

An improper authentication vulnerability in the authentication module of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Implement multi-factor authentication, enforce strong password policies, use proven authentication frameworks.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Improper Authentication (CWE-287), which allows attackers to bypass authentication mechanisms to gain unauthorized access. An improper authentication vulnerability in the authentication module of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to obtain system information by sending a crafted URL to a vulnerable device. Affected products include: Zyxel Nas326 Firmware, Zyxel Nas542 Firmware.

Know when Nas326 Firmware gets its next vulnerability

Watch products and get an email when something new is published
Check this CVE against your own stack and servers
Exploit and PoC references, threat intelligence from 22 sources

Continue with Google Continue with GitHub

No credit card · 7-day full trial

Severity by source

NVD PRIMARY 7.5 HIGH

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

DescriptionNVD

An improper authentication vulnerability in the authentication module of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to obtain system information by sending a crafted URL to a vulnerable device.

Threat Intelligence Overview

EPSS Score

0.9%

Top 46% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.9%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +38

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)NVD

cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:zyxel:nas542_firmware:*:*:*:*:*:*:*:*

More in Nas326 Firmware

View all

CVE-2020-9054 CRITICAL Emergency POC

9.8 Mar 04

Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21 contain a pre-authentication command

CVE-2024-29974 CRITICAL Act Now POC

9.8 Jun 04

** UNSUPPORTED WHEN ASSIGNED ** The remote code execution vulnerability in the CGI program “file_upload-cgi” in Zyxel NA

CVE-2024-29973 CRITICAL Act Now POC

9.8 Jun 04

** UNSUPPORTED WHEN ASSIGNED ** The command injection vulnerability in the “setCookie” parameter in Zyxel NAS326 firmwar

CVE-2024-29972 CRITICAL Act Now POC

9.8 Jun 04

** UNSUPPORTED WHEN ASSIGNED ** The command injection vulnerability in the CGI program "remote_help-cgi" in Zyxel NAS326

CVE-2019-10633 HIGH This Week POC

8.8 Apr 09

An eval injection vulnerability in the Python web server routing on the Zyxel NAS 326 version 5.21 and below allows a re

CVE-2019-10631 HIGH This Week POC

8.8 Apr 09

Shell Metacharacter Injection in the package installer on Zyxel NAS 326 version 5.21 and below allows an authenticated a

CVE-2019-10630 HIGH This Week POC

8.8 Apr 09

A plaintext password vulnerability in the Zyxel NAS 326 through 5.21 allows an elevated privileged user to get the admin

CVE-2024-29975 MEDIUM This Month POC

6.7 Jun 04

** UNSUPPORTED WHEN ASSIGNED ** The improper privilege management vulnerability in the SUID executable binary in Zyxel N

CVE-2024-29976 MEDIUM This Month POC

6.5 Jun 04

** UNSUPPORTED WHEN ASSIGNED ** The improper privilege management vulnerability in the command “show_allsessions” in Zyx

CVE-2019-10632 MEDIUM This Month POC

6.5 Apr 09

A directory traversal vulnerability in the file browser component on the Zyxel NAS 326 version 5.21 and below allows a l

CVE-2024-6342 CRITICAL Act Now

9.8 Sep 10

**UNSUPPORTED WHEN ASSIGNED** A command injection vulnerability in the export-cgi program of Zyxel NAS326 firmware versi

CVE-2023-4474 CRITICAL Act Now

9.8 Nov 30

The improper neutralization of special elements in the WSGI server of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0

Same weakness CWE-287 – Improper Authentication

View all

CVE-2022-40684 CRITICAL POC

9.8

CVE-2025-61882 CRITICAL POC

9.8

CVE-2020-0688 HIGH POC

8.8

CVE-2023-46805 HIGH POC

8.2

CVE-2023-35078 CRITICAL POC

9.8

CVE-2015-1187 CRITICAL POC

9.8

CVE-2024-7593 CRITICAL POC

9.8

CVE-2017-7921 CRITICAL POC

9.8

Same technique Authentication Bypass

View all

CVE-2015-3306 CRITICAL POC

10.0

CVE-2023-22515 CRITICAL POC

9.8

CVE-2012-4681 CRITICAL POC

9.8

CVE-2013-2465 CRITICAL POC

9.8

CVE-2011-3544 CRITICAL POC

9.8

CVE-2024-0012 CRITICAL POC

9.3

References

Advisories & patches

PATCH https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-products

Search Externally

GitHub PoC

Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC

Back