Service impersonation via duplicate principal names
Published Nov 10, 2021 · Updated Aug 19, 2026
Privilege escalation in Active Directory Domain Services on affected Windows Server builds allows remote authenticated users to impersonate services. Active Directory permits nonadministrators to assign duplicate UPNs, SPNs, or alias-equivalent SPNs instead of enforcing forest-wide uniqueness. A domain account with attribute-write rights can redirect Kerberos authentication to a controlled computer, enabling service impersonation and resulting access.
Summary
What happened
Privilege escalation in Active Directory Domain Services on affected Windows Server builds allows remote authenticated users to impersonate services. Active Directory permits nonadministrators to assign duplicate UPNs, SPNs, or alias-equivalent SPNs instead of enforcing forest-wide uniqueness. A domain account with attribute-write rights can redirect Kerberos authentication to a controlled computer, enabling service impersonation and resulting access.
The record
- CVE
- CVE-2021-42282
- Published
- Nov 10, 2021
- Updated
- Aug 19, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-269, T1557
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Nov 10, 2021CVE publishedPublication date reported by the CVE source.
- Aug 19, 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.
- Affected versionversion=10.0.17763.0 <10.0.17763.2300
What conditions does exploitation require?
What is affected?
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.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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