CVE-2025-26647Network attack vector

Privilege escalation via unchecked certificate authority trust

Published Apr 8, 2025 · Updated Aug 10, 2026

Improper input validation in Windows Kerberos allows remote authenticated users to elevate privileges through certificate-based authentication. A Windows KDC accepts a valid certificate whose issuing authority is trusted but absent from the NTAuth store when an SKI mapping appears in the principal's altSecID attribute. Exploitation requires control of an account and a matching certificate-mapping configuration, and successful authentication grants the mapped principal's privileges.

CVSS severity8.8
High
EPSS probability2.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Windows Kerberos allows remote authenticated users to elevate privileges through certificate-based authentication. A Windows KDC accepts a valid certificate whose issuing authority is trusted but absent from the NTAuth store when an SKI mapping appears in the principal's altSecID attribute. Exploitation requires control of an account and a matching certificate-mapping configuration, and successful authentication grants the mapped principal's privileges.

The record

CVE
CVE-2025-26647
Published
Apr 8, 2025
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-20, T1068
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 8, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 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=10.0.17763.0 <10.0.17763.7136

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.7136
Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.3775
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.7969
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.25423
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.25423
Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation)version=10.0.25398.0 <10.0.25398.1551
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.7969
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.7601.0 <6.1.7601.27670
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.1.7601.0 <6.1.7601.27670
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.22523
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.7136
Microsoft · Windows Server 2008 Service Pack 2version=6.0.6003.0 <6.0.6003.23220
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.3453
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.3775
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.22523
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.6003.0 <6.0.6003.23220

Published CVSS scores

8.8Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
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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