Which products and versions are affected by CVE-2023-27992?

Affected: NAS326 firmware (Zyxel) versions >= = = < V5.21(ABAG.11)C0. The full list is in the CVE brief.

Is CVE-2023-27992 being exploited in the wild?

It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 23, 2023.

Is CVE-2023-27992 in the CISA KEV catalog?

Yes. It was added on Jun 23, 2023 with a federal remediation due date of Jul 14, 2023.

Is there a public exploit for CVE-2023-27992?

Public exploit code is available.

How urgently should CVE-2023-27992 be patched?

Brandefense priority: patch immediately, because it is listed as exploited in the wild.

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Vulnerability Intelligence

CVE-2023-27992

Q: Is CVE-2023-27992 being exploited in the wild?

It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 23, 2023.

Q: Is CVE-2023-27992 in the CISA KEV catalog?

Yes. It was added on Jun 23, 2023 with a federal remediation due date of Jul 14, 2023.

Q: Is there a public exploit for CVE-2023-27992?

Public exploit code is available.

Q: Is there a fix for CVE-2023-27992?

Fixed versions are available, including NAS326 firmware 5.21\(aazf.14\)c0, NAS540 firmware 5.21\(aatb.11\)c0, NAS542 firmware 5.21\(abag.11\)c0.

Q: How urgently should CVE-2023-27992 be patched?

Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CriticalExploitedPublic exploit

The pre-authentication command injection vulnerability in the Zyxel NAS326 firmware versions prior to V5.21(AAZF.14)C0, NAS540 firmware versions prior to V5.21(AATB.11)C0, and NAS542 firmware versions prior to V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute…

Published Jun 20, 2023 · Updated Oct 21, 2025 · Also known as TR-23-0368

Key Facts

Patch immediately

CVE-2023-27992 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting NAS326 firmware (Zyxel), NAS540 firmware (Zyxel), NAS542 firmware (Zyxel).
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 23, 2023. Public exploit code is available.
EPSS estimates a 83% probability of exploitation in the next 30 days.
Fixed versions are available, including NAS326 firmware 5.21\(aazf.14\)c0, NAS540 firmware 5.21\(aatb.11\)c0, NAS542 firmware 5.21\(abag.11\)c0.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CVSS v3.1

9.8

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS (30-day exploit likelihood)

83%

Higher than 99.6% of all scored CVEs

Exploited in the wild

Yes

4 catalog listings

Public exploit code

Available

Proof-of-concept or weaponized module

Get the full CVE-2023-27992 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

Known-Exploited Catalog Listings

Catalog	Added	Remediation due	Ransomware use
CISA KEV	Jun 23, 2023	Jul 14, 2023	Not reported
Industry KEV feed	Jun 23, 2023	Jul 14, 2023	Not reported
CIRCL KEV	Jun 23, 2023	Jul 14, 2023	Not reported
ENISA EUVD	Jun 23, 2023	n/a	Not reported

Required action: Apply updates per vendor instructions.

Affected Products

6 affected entries in total

Product	Affected versions	Fixed in
NAS326 firmwareZyxel	>= < V5.21(AAZF.14)C0	5.21\(aazf.14\)c0
NAS540 firmwareZyxel	>= < V5.21(AATB.11)C0	5.21\(aatb.11\)c0
NAS542 firmwareZyxel	>= < V5.21(ABAG.11)C0	5.21\(abag.11\)c0

Patched Releases

NAS326 firmware

5.21\(aazf.14\)c0

NAS540 firmware

5.21\(aatb.11\)c0

NAS542 firmware

5.21\(abag.11\)c0

Timeline

Publicly disclosed
Jun 20, 2023
Added to CISA KEV
Jun 23, 2023
Added to Industry KEV feed
Jun 23, 2023
Added to CIRCL KEV
Jun 23, 2023
Added to ENISA EUVD
Jun 23, 2023
Last updated
Oct 21, 2025

Weakness Type

CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

References

7 more references in the full CVE brief

FAQ

Common Questions.

The pre-authentication command injection vulnerability in the Zyxel NAS326 firmware versions prior to V5.21(AAZF.14)C0, NAS540 firmware versions prior to V5.21(AATB.11)C0, and NAS542 firmware versions prior to V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands remot…
Affected: NAS326 firmware (Zyxel) versions >= < V5.21(AAZF.14)C0; NAS540 firmware (Zyxel) versions >= < V5.21(AATB.11)C0; NAS542 firmware (Zyxel) versions >= < V5.21(ABAG.11)C0. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 23, 2023.
Yes. It was added on Jun 23, 2023 with a federal remediation due date of Jul 14, 2023.
Public exploit code is available.
Fixed versions are available, including NAS326 firmware 5.21\(aazf.14\)c0, NAS540 firmware 5.21\(aatb.11\)c0, NAS542 firmware 5.21\(abag.11\)c0.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

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