SYSTEM escalation via unchecked ALPC launch request
Published Jan 13, 2026 · Updated Jan 13, 2026
Improper privilege handling in Microsoft Windows Error Reporting allows local users to elevate privileges to SYSTEM through a crafted ALPC request. The SvcElevatedLaunch handler accepts shared-memory command-line data without adequately validating the caller's privileges, then starts WerFault.exe with that data. A low-privileged local account is required, and successful exploitation executes attacker-controlled code with SYSTEM privileges.
Summary
What happened
Improper privilege handling in Microsoft Windows Error Reporting allows local users to elevate privileges to SYSTEM through a crafted ALPC request. The SvcElevatedLaunch handler accepts shared-memory command-line data without adequately validating the caller's privileges, then starts WerFault.exe with that data. A low-privileged local account is required, and successful exploitation executes attacker-controlled code with SYSTEM privileges.
The record
- CVE
- CVE-2026-20817
- Published
- Jan 13, 2026
- Updated
- Jan 13, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2025 (Server Core installation)
- Classifications
- CWE-280, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jan 13, 2026CVE publishedPublication date reported by the CVE source.
- Jan 13, 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=10.0.26100.0 <10.0.26100.32230
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Windows Error Reporting ALPC privilege-escalation proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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