CVE-2020-13365

Original summary

Normalized public record · Updated Nov 3, 2026

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;

Publisher and source text is retained separately from QFinch interpretation.

Affected products

Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.

Remediation

Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.

1. Confirm the affected product and reachable code path exist in your environment.
2. Apply the vendor-supported patch or mitigation from the primary advisory.
3. Rescan the exact deployed revision and retain verification evidence.

Evidence coverage

SSVC priority

MEDIUM

Confidence

Not available

Aliases

None reported

Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.

Sources and record history

1. www.zyxel.com ↗
2. www.zyxel.com ↗

Record history

Published Aug 6, 2020 · Last refreshed Nov 3, 2026