Privilege escalation via SCM access-mask bypass
Published Apr 13, 2021 · Updated Aug 3, 2024
Improper authorization in Windows Services and Controller App allows remote authenticated users to start protected services. The SCM remote-access filter tests an explicit access mask, but a MAXIMUM_ALLOWED request reaches NtAccessCheckAndAuditAlarm and returns a service handle with SERVICE_START rights. A non-administrator account able to authenticate to SCM RPC is sufficient, and successful exploitation can control services with elevated privileges.
Summary
What happened
Improper authorization in Windows Services and Controller App allows remote authenticated users to start protected services. The SCM remote-access filter tests an explicit access mask, but a MAXIMUM_ALLOWED request reaches NtAccessCheckAndAuditAlarm and returns a service handle with SERVICE_START rights. A non-administrator account able to authenticate to SCM RPC is sufficient, and successful exploitation can control services with elevated privileges.
The record
- CVE
- CVE-2021-27086
- Published
- Apr 13, 2021
- Updated
- Aug 3, 2024
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-863, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 13, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=10.0.0 <publication
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.
Weakness, pattern, technique
Public exploit references
- Windows SCM Remote Access Check Limit Bypass proof of conceptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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