CVE-2020-13364

HIGH
8.8
CVSS Score
Published: August 6, 2020 at 04:54 PM UTC
Updated: June 17, 2026 at 02:53 AM UTC
8 products affected across 1 vendorNAS326 firmwareNAS542 firmwareNAS540 firmware

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Severity
HIGH8.8
Exploit prediction
EPSS 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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < v5.21(aazf.9)c0
Affected range stops below v5.21(aazf.9)c0, so it looks safe — our inference, not a vendor statement
zyxel-nas326 (same device)
v < v5.21(aasz.5)c0
Affected range stops below v5.21(aasz.5)c0, so it looks safe — our inference, not a vendor statement
zyxel-nas520 (same device)
v < v5.21(aatb.6)c0
Affected range stops below v5.21(aatb.6)c0, so it looks safe — our inference, not a vendor statement
zyxel-nas540 (same device)
v < v5.21(abag.6)c0
Affected range stops below v5.21(abag.6)c0, so it looks safe — our inference, not a vendor statement
zyxel-nas542 (same device)
All versions
All versions
All versions
All versions

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
NVD-CWE-noinfo

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