Main Vulnerability Database Vulnerabilities #VU121246

Permissions, Privileges, and Access Controls in Microsoft Windows and Windows Server - CVE-2026-20817

Published: January 13, 2026 / Updated: February 27, 2026

Vulnerability identifier: #VU121246

CSH Severity: Low

CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-20817

CWE-ID: CWE-264

Exploitation vector: Local access

Exploit availability: Public exploit is available

Vulnerability details

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to application does not properly impose security restrictions in Windows Error Reporting Service, which leads to security restrictions bypass and privilege escalation.

Affected software

Microsoft Windows
Windows Server

How to mitigate CVE-2026-20817

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.6809, 10 22H2 10.0.19045.6809, 10 1607 10.0.14393.8783, 11 23H2 10.0.22631.6491, 11 24H2 10.0.26100.7623
Windows Server - addressed in versions 2022 23H2 10.0.25398.2092, 2022 10.0.20348.4648, 2025 10.0.26100.7623, 2025 10.0.26100.32230

Links to Public Exploits and PoC-codes

Exploit #12456 - CVE-2026-20817 (Windows Error Reporting ALPC Elevation of Privilege (CVE-2026-20817) - Proof-of-Concept exploit demonstrating local privilege escalation via WER service. ) (February 27, 2026)

External References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20817

Related Security Bulletins

Privilege escalation in Microsoft Windows Error Reporting Service