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CVE-2026-25187 Microsoft CVE debrief

A local privilege escalation vulnerability exists in Microsoft Winlogon due to improper link resolution before file access (CWE-59). An authorized attacker with local access can exploit this flaw to elevate privileges on affected Windows systems. The vulnerability carries a CVSS 3.1 score of 7.8 (HIGH severity) with an attack vector of local, low attack complexity, and low privileges required. No user interaction is needed for exploitation. Microsoft has addressed this vulnerability through security updates, with patch versions specified across multiple Windows 10, Windows 11, and Windows Server releases. The CVE was initially published on March 10, 2026, and subsequently modified on May 26, 2026. This vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, and no known ransomware campaign use has been documented.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-10
Original CVE updated
2026-05-26
Advisory published
2026-03-10
Advisory updated
2026-05-26

Who should care

System administrators managing Windows endpoints and servers, security operations teams monitoring for privilege escalation activity, and organizations with shared workstation environments or insufficient privilege separation controls

Technical summary

The vulnerability stems from Winlogon's improper handling of symbolic links or junctions before accessing files, allowing an attacker with local access to manipulate file paths and gain elevated privileges. The attack requires local access and low privileges but no user interaction. Successful exploitation grants high impact across confidentiality, integrity, and availability. Affected platforms span Windows 10 (versions 1607 through 22H2), Windows 11 (versions 23H2 through 26H1), and Windows Server (2012 through 2025), with specific security update boundaries defined for each. The fix involves proper link resolution checks before file operations in the Winlogon process.

Defensive priority

high

Recommended defensive actions

  • Apply Microsoft security updates to affected Windows systems, ensuring versions meet or exceed the specified patch levels for each OS release
  • Prioritize patching on systems where multiple users have interactive logon access or where least-privilege principles are not fully enforced
  • Review systems for unauthorized privilege escalation activity, particularly around Winlogon-related processes
  • Consider implementing additional access controls to restrict local logon capabilities where not required for business operations
  • Monitor for detection scripts and mitigation guidance from security vendors to supplement patching efforts

Evidence notes

CWE-59 (Improper Link Resolution Before File Access) identified by Microsoft as the root cause. CVSS vector confirms local attack vector with high impact on confidentiality, integrity, and availability. CPE criteria enumerate affected Windows versions with specific patch boundaries.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-25187 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-25187

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-25187 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-25187

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-25187

    [email protected] - Vendor Advisory

  • Source reference

    Unverified legacy reference

    URL: https://www.vicarius.io/vsociety/posts/cve-2026-25187-detection-script-winlogon-elevation-of-privilege-vulnerability

    af854a3a-2127-422b-91ae-364da2661108

  • Source reference

    Unverified legacy reference

    URL: https://www.vicarius.io/vsociety/posts/cve-2026-25187-mitigation-script-winlogon-elevation-of-privilege-vulnerability

    af854a3a-2127-422b-91ae-364da2661108

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.