Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2024-21899

QTS, QuTS hero, QuTScloud

QNAP / QTS · affected before 5.1.3.2578 build 20231110

Watch CVE-2024-21899 Browse KEV feed
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. Previdian tracks this CVE as a known exploited vulnerability. Confidence is high. Also confirmed by third-party sources.

Who is affected?

QNAP / 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

qnap Affected
qts
Before 5.1.3.2578 build 20231110 Before 4.5.4.2627 build 20231225
qnap Affected
quts_hero
Before h5.1.3.2578 build 20231110 Before h4.5.4.2626 build 20231225
qnap Affected
qutscloud
Before c5.1.5.2651
QNAP Systems Inc. Affected
QTS
Before 5.1.3.2578 build 20231110 Before 4.5.4.2627 build 20231225
QNAP Systems Inc. Affected
QuTS hero
Before h5.1.3.2578 build 20231110 Before h4.5.4.2626 build 20231225
QNAP Systems Inc. Affected
QuTScloud
Before c5.1.5.2651
Published
08 Mar 2024
Exploitation Reported
27 Apr 2025
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

windows

CVE References

Exploitation evidence

Why Previdian 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

A trusted third party reported exploitation.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian 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
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian 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

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

24.4%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Authentication CWE-287

Timeline

From disclosure to observed exploitation

  1. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  2. 16:17 UTC

    CVE published

    Vulnerability disclosed publicly

  3. 02:31 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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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

Sample API response 
{
  "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 }
}