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HIGH · 7.5

CVE-2026-20921

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.

Vulnerability Description

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH

Affected Products

VendorProductVersions
MicrosoftWindows 10 1607< 10.0.14393.8783
MicrosoftWindows 10 1809< 10.0.17763.8276
MicrosoftWindows 10 21H2< 10.0.19044.6809
MicrosoftWindows 10 22H2< 10.0.19045.6809
MicrosoftWindows 11 23H2< 10.0.22631.6491
MicrosoftWindows 11 24H2< 10.0.26100.7623
MicrosoftWindows 11 25H2< 10.0.26200.7623
MicrosoftWindows Server 2008-
MicrosoftWindows Server 2012-
MicrosoftWindows Server 2016< 10.0.14393.8783
MicrosoftWindows Server 2019< 10.0.17763.8276
MicrosoftWindows Server 2022< 10.0.20348.4648
MicrosoftWindows Server 2022 23H2< 10.0.25398.2092
MicrosoftWindows Server 2025< 10.0.26100.32230

Related Weaknesses (CWE)

CWE-362

References

FAQ

What is CVE-2026-20921?

CVE-2026-20921 is a vulnerability with a CVSS score of 7.5 (HIGH). Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.

How severe is CVE-2026-20921?

CVE-2026-20921 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-20921?

Check the references section above for vendor advisories and patch information. Affected products include: Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21H2, Microsoft Windows 10 22H2, Microsoft Windows 11 23H2.