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CVE-2026-20877 Microsoft CVE debrief

CVE-2026-20877 is a use-after-free vulnerability in Windows Management Services, allowing an authorized attacker to elevate privileges locally. The vulnerability affects multiple Windows versions, including Windows 10, Windows 11, and Windows Server editions. Microsoft has provided a CVSS score of 7.8, rating it as HIGH severity. The CVE record was published on 2026-01-13T18:16:17.813Z and has not been modified since then. System administrators and security teams responsible for Windows Management Services installations should be aware of CVE-2026-20877. Due to the HIGH severity and local privilege escalation potential, immediate review and mitigation are recommended. It is essential to review and apply Microsoft's vendor advisory for CVE-2026-20877, inventory Windows Management Services installations for potential exposure, implement compensating controls to limit local privilege escalation, and monitor for suspicious activity related to Windows Management Services.

Vendor
Microsoft
Product
Windows 10 Version 1809
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-01-13
Original CVE updated
2026-07-30
Advisory published
2026-01-13
Advisory updated
2026-07-30

Who should care

System administrators and security teams responsible for Windows Management Services installations should be aware of CVE-2026-20877. Due to the HIGH severity and local privilege escalation potential, immediate review and mitigation are recommended.

Technical summary

CVE-2026-20877 is a use-after-free vulnerability in Windows Management Services. An authorized attacker can exploit this vulnerability to elevate privileges locally. The vulnerability affects multiple Windows versions, including Windows 10, Windows 11, and Windows Server editions. Microsoft has provided a CVSS score of 7.8, rating it as HIGH severity.

Defensive priority

CVE-2026-20877 is rated HIGH with a CVSS score of 7.8, indicating a significant elevation of privileges risk locally. Affected Windows versions require immediate review.

Recommended defensive actions

  • Review and apply Microsoft's vendor advisory for CVE-2026-20877
  • Inventory Windows Management Services installations for potential exposure
  • Implement compensating controls to limit local privilege escalation
  • Monitor for suspicious activity related to Windows Management Services

Evidence notes

The CVE-2026-20877 record indicates a use-after-free vulnerability in Windows Management Services, allowing an authorized attacker to elevate privileges locally. Multiple Windows versions are affected, including Windows 10, Windows 11, and Windows Server editions. Microsoft has provided a vendor advisory for mitigation.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-20877 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-20877

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

  • CVE-2026-20877 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-20877

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

Supplemental references

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.