VulnerabilityAnalyzed

CVE-2026-27921

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

HIGH 7.0EPSS 1.19%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (1.19%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

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

CVSS 3.1: 7.0 HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS: 1.19% probability · 66th percentile
CISA KEV: Not listed
Weakness: CWE-362, CWE-416
Affected: microsoft/windows 10 1607 · 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 2012 · microsoft/windows server 2016 · microsoft/windows server 2019 · microsoft/windows server 2022 · microsoft/windows server 2022 23h2 · microsoft/windows server 2025
Source: secure@microsoft.com

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-27921Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.