What is CVE-2023-27992?

CVE-2023-27992 is a critical-severity vulnerability in Zyxel Nas326, classified under OS Command Injection. CVSS score: 9.8/10. Published 2023-06-19.

How severe is CVE-2023-27992?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2023-27992 known to be exploited?

Yes. CVE-2023-27992 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-06-23), indicating it is being actively exploited. 3 public proof-of-concept repositories are indexed.

RCE in Zyxel Nas326

CVE-2023-27992

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 remotely by sending a crafted HTTP request.

Vulnerability class: Command Injection (OS Command Injection)

Published 2023-06-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.828 (99.7th percentile), scored 2026-10-16.

High probability of exploitation in the next 30 days — patch promptly. 100th percentile — 99.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.838 · newest: 0.828 · change: -0.010

Affected products

Zyxel Nas326
Zyxel Nas326 Firmware — versions < V5.21(AAZF.14)C0
Zyxel Nas326 Firmware
Zyxel Nas540
Zyxel Nas540 Firmware — versions < V5.21(AATB.11)C0
Zyxel Nas540 Firmware
Zyxel Nas542
Zyxel Nas542 Firmware — versions < V5.21(ABAG.11)C0
Zyxel Nas542 Firmware

Weakness classification (CWE)

CWE-78 — OS Command Injection

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2023-06-23. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2023-07-14.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for… (Patch, Vendor Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2023-27992?: CVE-2023-27992 is a critical-severity vulnerability in Zyxel Nas326, classified under OS Command Injection. CVSS score: 9.8/10. Published 2023-06-19.
How severe is CVE-2023-27992?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2023-27992 known to be exploited?: Yes. CVE-2023-27992 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-06-23), indicating it is being actively exploited. 3 public proof-of-concept repositories are indexed.