CVE-2025-21183

SYSTEM privilege escalation via ReFS double free

Published Feb 11, 2025 · Updated Feb 26, 2026

A double free in Microsoft Windows ReFS Deduplication Service before 10.0.26100.3194 allows local users to gain SYSTEM privileges. Microsoft identifies the affected service and duplicate memory release but has not disclosed the object, execution path, or input that triggers it. Exploitation requires local execution and a high-complexity condition, needs no prior privileges or user interaction, and grants complete system control.

CVSS severity7.4
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A double free in Microsoft Windows ReFS Deduplication Service before 10.0.26100.3194 allows local users to gain SYSTEM privileges. Microsoft identifies the affected service and duplicate memory release but has not disclosed the object, execution path, or input that triggers it. Exploitation requires local execution and a high-complexity condition, needs no prior privileges or user interaction, and grants complete system control.

The record

CVE
CVE-2025-21183
Published
Feb 11, 2025
Updated
Feb 26, 2026
Vendor
Microsoft
Product
Windows Server 2025 (Server Core installation)
Classifications
CWE-415, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.26100.0 <10.0.26100.3194

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.3194
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.3194
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.3194

Published CVSS scores

7.4Microsoft CorporationCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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