CVE-2026-20921: Windows SMB Server Elevation of Privilege Vulnerability
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
Other sources
Windows SMB Server Elevation of Privilege Vulnerability
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.1.7601.28117Patch KB5073699 - Upgrade
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Fixed in 6.3.9600.22968Patch KB5073696 - Upgrade
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Fixed in 6.2.9200.25868Patch KB5073698 - Upgrade
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Fixed in 6.0.6003.23717Patch KB5073700 - Upgrade
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Fixed in 10.0.26100.32230Patch KB5073379 - Upgrade
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Fixed in 10.0.26100.7623Patch KB5074109 - Upgrade
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Fixed in 10.0.25398.2092Patch KB5073450 - Upgrade
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Fixed in 10.0.14393.8783Patch KB5073722 - Upgrade
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Fixed in 10.0.22631.6491Patch KB5073455 - Upgrade
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Fixed in 10.0.26200.7623Patch KB5074109 - Upgrade
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Fixed in 10.0.20348.4648Patch KB5073457 - Upgrade
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Fixed in 10.0.19044.6809Patch KB5073724 - Upgrade
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Fixed in 10.0.19045.6809Patch KB5073724 - Upgrade
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Fixed in 10.0.17763.8276Patch KB5073723
Event History
Frequently Asked Questions
What is the severity of CVE-2026-20921?
The severity of CVE-2026-20921 is classified as high, indicating a significant risk to affected systems.
How do I fix CVE-2026-20921?
To fix CVE-2026-20921, apply the latest security patches provided by Microsoft for the affected Windows Server products.
Which versions of Windows are affected by CVE-2026-20921?
CVE-2026-20921 affects various versions of Windows Server including 2012 R2, 2012, 2008 R2, 2008, and several Windows 10 and 11 versions.
Can an attacker exploit CVE-2026-20921 without authentication?
No, an attacker must be an authorized user on the network to exploit CVE-2026-20921.
What type of attack does CVE-2026-20921 allow?
CVE-2026-20921 allows authorized attackers to elevate their privileges on affected systems through a race condition in the Windows SMB Server.