Is CVE-2024-21899 actively exploited?

Yes. KEV Intelligence tracks CVE-2024-21899 as a known exploited vulnerability. Confidence is high.

What exploitation activity has KEV Intelligence observed?

KEV Intelligence has not yet recorded sensor-observed exploitation attempts for CVE-2024-21899. Our sensors continue to monitor for activity targeting this CVE.

Which versions are affected?

CVE-2024-21899 affects QNAP Systems Inc. QTS and 2 other products. KEV Intelligence lists 10 version rows; examples include 5.1.0 to < 5.1.3.2578 build 20231110, 4.5.0 to < 4.5.4.2627 build 20231225, and h5.1.0 to < h5.1.3.2578 build 20231110.

No. CVE-2024-21899 is not currently listed in CISA KEV.

Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2024-21899

Q: How should organizations remediate it?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Q: Is it in CISA KEV?

No. CVE-2024-21899 is not currently listed in CISA KEV.

QTS, QuTS hero, QuTScloud

QNAP Systems Inc. / QTS · affected before 5.1.3.2578 build 20231110

View live feed Monitor via API Watch CVE

Severity: CVSS 9.8 · Critical
Confidence: High
Exploit status: Exploited in the wild
EPSS: 24.4%
First observed: —
Last observed: —

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2024-21899 is an unauthenticated QTS, QuTS hero, QuTScloud. An improper authentication vulnerability has been reported to affect several QNAP operating system versions. If exploited, the vulnerability could allow...

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is high.

Who is affected?

QNAP Systems Inc. / QTS affected before 5.1.3.2578 build 20231110.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

An improper authentication vulnerability has been reported to affect several QNAP operating system versions

An improper authentication vulnerability has been reported to affect several QNAP operating system versions. If exploited, the vulnerability could allow users to compromise the security of the system via a network.

We have already fixed the vulnerability in the following versions: QTS 5.1.3.2578 build 20231110 and later QTS 4.5.4.2627 build 20231225 and later QuTS hero h5.1.3.2578 build 20231110 and later QuTS hero h4.5.4.2626 build 20231225 and later QuTScloud c5.1.5.2651 and later

Vendor Product Affected Status

qnap qts Before 5.1.3.2578 build 20231110 Affected

qnap qts Before 4.5.4.2627 build 20231225 Affected

qnap quts_hero Before h5.1.3.2578 build 20231110 Affected

qnap quts_hero Before h4.5.4.2626 build 20231225 Affected

qnap qutscloud Before c5.1.5.2651 Affected

QNAP Systems Inc. QTS Before 5.1.3.2578 build 20231110 Affected

QNAP Systems Inc. QTS Before 4.5.4.2627 build 20231225 Affected

QNAP Systems Inc. QuTS hero Before h5.1.3.2578 build 20231110 Affected

QNAP Systems Inc. QuTS hero Before h4.5.4.2626 build 20231225 Affected

QNAP Systems Inc. QuTScloud Before c5.1.5.2651 Affected

Published: 08 Mar 2024
Exploitation Reported: 27 Apr 2025
Attack vector: Remote
Complexity: Low
Privileges: None
User interaction: None

CVE References

CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2024-21899
qnap.com/en/security-advisory/qsa-24-09 qnap.com · CVE Record https://www.qnap.com/en/security-advisory/qsa-24-09

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

The Shadowserver

Recorded 27 Apr 2025

Independent exploitation attestation added to the KEV Intelligence record.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

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Source	Added
The Shadowserver First	2025-04-27 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets: 0
User-Agents: 0

Raw values available in Pro and Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

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

EPSS

24.4%

Weaknesses

Improper Authentication CWE-287

Timeline

From disclosure to observed exploitation

27 Apr 2025
Added to KEV Intelligence KEV Feed

High-confidence, third-party attested exploitation
08 Mar 2024
CVE published

Vulnerability disclosed publicly
03 Jan 2024
CVE ID reserved

Identifier reserved by the CNA

Pro API

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Evidence confidence and provenance
First-party sensor telemetry
PoC and scanner references
Affected versions and enrichment
Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2024-21899

Free JSON includes basic KEV fields

{
  "cve_id": "CVE-2024-21899",
  "confidence": "High",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.24365,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

Early warning alerts

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