CASCACascade Atlas

Evidence dossier

CVE-2023-27992

CVE-2023-27992

82.9–97.9Priority evidence range
As known Jul 19, 2026, 5:00 AM UTCgen-56ccdaf9

Normalized restatement

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.

State
PUBLISHED
Published
Jun 19, 2023
Updated
Oct 21, 2025
Evidence coverage
85%
CISA KEVCatalog member

Apply updates per vendor instructions.

FIRST EPSS84.19%

2026-07-18 · v2026.06.15 · percentile 99.7%

Source stateNo scored conflict

Distinct CVSS assessments remain side by side; none are averaged.

Source comparison

Who said what

CISA-ADPindependent enrichment
container

CISA ADP Vulnrichment

CVEderivative copy
container

CVE Program Container

Zyxeloriginal assertion
container

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.

CISA KEVoriginal assertion
observed_exploitation

Zyxel Multiple NAS Devices Command Injection Vulnerability

FIRST EPSSoriginal assertion
model_probability

Probability 0.841950000000; percentile 0.996680000000

Applicability

Cited product scope

Trace impact →
ZyxelNAS326 firmware
[{"status": "affected", "version": "< V5.21(AAZF.14)C0"}]unknown
ZyxelNAS540 firmware
[{"status": "affected", "version": "< V5.21(AATB.11)C0"}]unknown
ZyxelNAS542 firmware
[{"status": "affected", "version": "< V5.21(ABAG.11)C0"}]unknown
Unknown vendorUnknown product
cpe:2.3:h:zyxel:nas326:-:*:*:*:*:*:*:*constrained
Unknown vendorUnknown product
cpe:2.3:h:zyxel:nas540:-:*:*:*:*:*:*:*constrained
Unknown vendorUnknown product
cpe:2.3:h:zyxel:nas542:-:*:*:*:*:*:*:*constrained
Unknown vendorUnknown product
cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*; end excluding 5.21\(aazf.14\)c0supported
Unknown vendorUnknown product
cpe:2.3:o:zyxel:nas540_firmware:*:*:*:*:*:*:*:*; end excluding 5.21\(aatb.11\)c0supported
Unknown vendorUnknown product
cpe:2.3:o:zyxel:nas542_firmware:*:*:*:*:*:*:*:*; end excluding 5.21\(abag.11\)c0supported

Assessments

CVSS by origin

9.8
security@zyxel.com.twCVSS 3.1 · role SecondaryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8
ZyxelCVSS 3.1 · role unknownCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Limitations and unknowns

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; unresolved scope remains unknown.
  • NVD-carried upstream facts remain derivative and are not independent corroboration.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Factor D is unknown in Public Core because no accepted canonical mapping-obligation ledger is present.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.