What is CVE-2026-42991?

CVE-2026-42991 is a high-severity vulnerability in Microsoft Windows_10_1809, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.8/10. Published 2026-06-09.

How severe is CVE-2026-42991?

High severity. CVSS v3 base score is 7.8 out of 10.

Use After Free in Microsoft Windows_10_1809

CVE-2026-42991

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Push Notifications allows an authorized attacker to elevate privileges locally.

Vulnerability class: Race Condition

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H.

Affected products

Microsoft Windows_10_1809
Microsoft Windows_10_21h2
Microsoft Windows_10_22h2
Microsoft Windows_11_23h2
Microsoft Windows_11_24h2
Microsoft Windows_11_25h2
Microsoft Windows_11_26h1
Microsoft Windows_server_2019
Microsoft Windows_server_2022
Microsoft Windows_server_2025

Weakness classification (CWE)

CWE-362 — Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition)
CWE-416 — Use After Free

References

secure@microsoft.com (Vendor Advisory)

Frequently asked questions

What is CVE-2026-42991?: CVE-2026-42991 is a high-severity vulnerability in Microsoft Windows_10_1809, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.8/10. Published 2026-06-09.
How severe is CVE-2026-42991?: High severity. CVSS v3 base score is 7.8 out of 10.