Local privilege escalation via arbitrary COM initialization
Published Feb 10, 2026 · Updated Feb 10, 2026
Improper authentication in Microsoft Windows Storage allows local users to execute code with LOCAL SERVICE privileges through COM hijacking. Windows_Storage!CinstClassFactory::CreateInstance reads a CLSID from a user-writable HKCU key, and _SHCoCreateInstance loads its InprocServer32 DLL from a user-writable ProgramData path. The demonstrated path requires low-privilege local access, an attached USB drive containing a JPEG, and Windows Media Player; it reaches LOCAL SERVICE, while SYSTEM escalation requires an additional technique.
Summary
What happened
Improper authentication in Microsoft Windows Storage allows local users to execute code with LOCAL SERVICE privileges through COM hijacking. Windows_Storage!CinstClassFactory::CreateInstance reads a CLSID from a user-writable HKCU key, and _SHCoCreateInstance loads its InprocServer32 DLL from a user-writable ProgramData path. The demonstrated path requires low-privilege local access, an attached USB drive containing a JPEG, and Windows Media Player; it reaches LOCAL SERVICE, while SYSTEM escalation requires an additional technique.
The record
- CVE
- CVE-2026-21508
- Published
- Feb 10, 2026
- Updated
- Feb 10, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-426, CWE-287, T1068, T1574.001
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 10, 2026CVE publishedPublication date reported by the CVE source.
- Feb 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.
- Affected versionversion=10.0.17763.0 <10.0.17763.8389
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
- 0xc4r CVE-2026-21508 proof of conceptproof of concept · demonstrated
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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