CVE-2020-13364

HIGH

Zyxel NAS/NSA Devices - Unauthenticated Remote TELNET Access via Backdoor CGI

Title source: llm
STIX 2.1

Description

A backdoor in certain Zyxel products allows remote TELNET access via a CGI script. 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.

References (2)

Core 2

Scores

CVSS v3 8.8
EPSS 0.0024
EPSS Percentile 46.3%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Details

Status published
Products (4)
zyxel/nas326_firmware < v5.21\(aazf.9\)c0
zyxel/nas520_firmware < v5.21\(aasz.5\)c0
zyxel/nas540_firmware < v5.21\(aatb.6\)c0
zyxel/nas542_firmware < v5.21\(abag.6\)c0
Published Aug 06, 2020
Tracked Since Feb 18, 2026