Nas326 Firmware
CVE-2020-13365
HIGH
Vulnerability Assessment
| Weakness |
CWE
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. |
| Impact | CVSS score of 8.8 (HIGH). Attack characteristics: network attack vector, low complexity, low 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. |
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Alert meAnalysisAI
Certain Zyxel products have a locally accessible binary that allows a non-root user to generate a password for an undocumented user account that can be used for a TELNET session as root. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Implement multi-factor authentication, enforce strong password policies, use proven authentication frameworks.
Affects your stack
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Technical ContextAI · show details
This vulnerability is classified as Improper Authentication (CWE-287), which allows attackers to bypass authentication mechanisms to gain unauthorized access. Certain Zyxel products have a locally accessible binary that allows a non-root user to generate a password for an undocumented user account that can be used for a TELNET session as root. This affects NAS520 V5.21(AASZ.4)C0, V5.21(AASZ.0)C0, V5.11(AASZ.3)C0, and V5.11(AASZ.0)C0; NAS542 V5.11(ABAG.0)C0, V5.20(ABAG.1)C0, and V5.21(ABAG.3)C0; NSA325 v2_V4.81(AALS.0)C0 and V4.81(AAAJ.1)C0; NSA310 4.22(AFK.0)C0 and 4.22(AFK.1)C0; NAS326 V5.21(AAZF.8)C0, V5.11(AAZF.4)C0, V5.11(AAZF.2)C0, and V5.11(AAZF.3)C0; NSA310S V4.75(AALH.2)C0; NSA320S V4.75(AANV.2)C0 and V4.75(AANV.1)C0; NSA221 V4.41(AFM.1)C0; and NAS540 V5.21(AATB.5)C0 and V5.21(AATB.3)C0. Affected products include: Zyxel Nas326 Firmware, Zyxel Nas520 Firmware, Zyxel Nas540 Firmware, Zyxel Nas542 Firmware.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
Certain Zyxel products have a locally accessible binary that allows a non-root user to generate a password for an undocumented user account that can be used for a TELNET session as root. This affects NAS520 V5.21(AASZ.4)C0, V5.21(AASZ.0)C0, V5.11(AASZ.3)C0, and V5.11(AASZ.0)C0; NAS542 V5.11(ABAG.0)C0, V5.20(ABAG.1)C0, and V5.21(ABAG.3)C0; NSA325 v2_V4.81(AALS.0)C0 and V4.81(AAAJ.1)C0; NSA310 4.22(AFK.0)C0 and 4.22(AFK.1)C0; NAS326 V5.21(AAZF.8)C0, V5.11(AAZF.4)C0, V5.11(AAZF.2)C0, and V5.11(AAZF.3)C0; NSA310S V4.75(AALH.2)C0; NSA320S V4.75(AANV.2)C0 and V4.75(AANV.1)C0; NSA221 V4.41(AFM.1)C0; and NAS540 V5.21(AATB.5)C0 and V5.21(AATB.3)C0.
Threat Intelligence Overview
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.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)NVD
More in Nas326 Firmware
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Shell Metacharacter Injection in the package installer on Zyxel NAS 326 version 5.21 and below allows an authenticated a
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** UNSUPPORTED WHEN ASSIGNED ** The improper privilege management vulnerability in the SUID executable binary in Zyxel N
** UNSUPPORTED WHEN ASSIGNED ** The improper privilege management vulnerability in the command “show_allsessions” in Zyx
A directory traversal vulnerability in the file browser component on the Zyxel NAS 326 version 5.21 and below allows a l
**UNSUPPORTED WHEN ASSIGNED** A command injection vulnerability in the export-cgi program of Zyxel NAS326 firmware versi
The improper neutralization of special elements in the WSGI server of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0
GitHub PoC
Exploit-DB