CVE-2021-31958: Windows NTLM Elevation of Privilege Vulnerability

Severity: medium (CVSS 6.8 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-08 · updated 2026-06-17
Weakness: CWE-294

Description

Windows NTLM Elevation of Privilege Vulnerability

Affected products

Microsoft Windows 10 Version 1607: 20h2, 21h1, 1607, 1809, 1909, 2004
Microsoft Windows 7: all versions
Microsoft Windows 8.1: all versions
Microsoft Windows RT 8.1: all versions
Microsoft Windows Server 2008: r2-sp1, sp2
Microsoft Windows Server 2012: r2
Microsoft Windows Server 2016: 20h2, 1909, 2004
Microsoft Windows Server 2019: all versions
Microsoft Windows 10 Version 1507: from 10.0.0 before 10.0.10240.18967 — fixed in 10.0.10240.18967
Microsoft Windows 10 1607: from 10.0.0 before 10.0.14393.4467 — fixed in 10.0.14393.4467
Microsoft Windows 10: from 10.0.0 before 10.0.17763.1999 — fixed in 10.0.17763.1999
Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1621 — fixed in 10.0.18363.1621
Microsoft Windows 10 2004: from 10.0.0 before 10.0.19041.1052 — fixed in 10.0.19041.1052
Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19042.1052 — fixed in 10.0.19042.1052
Microsoft Windows 10 21H1: from 10.0.0 before 10.0.19043.1052 — fixed in 10.0.19043.1052
Microsoft Windows 7: from 6.1.0 before 6.1.7601.25632 — fixed in 6.1.7601.25632
Microsoft Windows 7 Service Pack 1: from 6.1.0 before 6.1.7601.25632 — fixed in 6.1.7601.25632
Microsoft Windows 8.1: from 6.3.0 before 6.3.9600.20045; from 6.3.0 before 6.3.9600.20044 — fixed in 6.3.9600.20045, 6.3.9600.20044
Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.0 before 6.1.7601.25632 — fixed in 6.1.7601.25632
Microsoft Windows Server 2008 Service Pack 2: from 6.0.0 before 6.0.6003.21137 — fixed in 6.0.6003.21137
Microsoft Windows Server 2012: from 6.2.0 before 6.2.9200.23372 — fixed in 6.2.9200.23372
Microsoft Windows Server 2012 R2: from 6.3.0 before 6.3.9600.20045; from 6.3.0 before 6.3.9600.20044 — fixed in 6.3.9600.20045, 6.3.9600.20044
Microsoft Windows Server 2016: from 10.0.0 before 10.0.14393.4467 — fixed in 10.0.14393.4467
Microsoft Windows Server 2019: from 10.0.0 before 10.0.17763.1999 — fixed in 10.0.17763.1999
Microsoft Windows Server version 2004: from 10.0.0 before 10.0.19041.1052 — fixed in 10.0.19041.1052
Microsoft Windows Server version 20H2: from 10.0.0 before 10.0.19042.1052 — fixed in 10.0.19042.1052

How to fix

Upgrade to a fixed version: Microsoft Windows 10 Version 1507 10.0.10240.18967; Microsoft Windows 10 1607 10.0.14393.4467; Microsoft Windows 10 10.0.17763.1999; Microsoft Windows 10 1909 10.0.18363.1621; Microsoft Windows 10 2004 10.0.19041.1052; Microsoft Windows 10 20H2 10.0.19042.1052; Microsoft Windows 10 21H1 10.0.19043.1052; Microsoft Windows 7 6.1.7601.25632; Microsoft Windows 7 Service Pack 1 6.1.7601.25632; Microsoft Windows 8.1 6.3.9600.20045, 6.3.9600.20044; Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25632; Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21137. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-31958 or the next vulnerability affects your stack