CVE-2021-33765: Windows Installer Spoofing Vulnerability

Severity: low (CVSS 2.1 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-07-14 · updated 2026-08-10

Description

Windows Installer Spoofing 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: all versions
Microsoft Windows Server 2012: all versions
Microsoft Windows Server 2016: 20h2, 2004
Microsoft Windows Server 2019: all versions
Microsoft Windows 10 Version 1507: from 10.0.10240.0 before 10.0.10240.19003 — fixed in 10.0.10240.19003
Microsoft Windows 10 1607: from 10.0.14393.0 before 10.0.14393.4530 — fixed in 10.0.14393.4530
Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.2061 — fixed in 10.0.17763.2061
Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1679 — fixed in 10.0.18363.1679
Microsoft Windows 10 2004: from 10.0.0 before 10.0.19041.1110 — fixed in 10.0.19041.1110
Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19042.1110 — fixed in 10.0.19042.1110
Microsoft Windows 10 21H1: from 10.0.0 before 10.0.19043.1110 — fixed in 10.0.19043.1110
Microsoft Windows 7: from 6.1.0 before 6.1.7601.25661 — fixed in 6.1.7601.25661
Microsoft Windows 7 Service Pack 1: from 6.1.0 before 6.1.7601.25661 — fixed in 6.1.7601.25661
Microsoft Windows 8.1: from 6.3.0 before 6.3.9600.20069 — fixed in 6.3.9600.20069
Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.7601.0 before 6.1.7601.25661 — fixed in 6.1.7601.25661
Microsoft Windows Server 2008 Service Pack 2: from 6.0.6003.0 before 6.0.6003.21167 — fixed in 6.0.6003.21167
Microsoft Windows Server 2012: from 6.2.9200.0 before 6.2.9200.23409 — fixed in 6.2.9200.23409
Microsoft Windows Server 2012 R2: from 6.3.9600.0 before 6.3.9600.20069 — fixed in 6.3.9600.20069
Microsoft Windows Server 2016: from 10.0.14393.0 before 10.0.14393.4530 — fixed in 10.0.14393.4530
Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.2061 — fixed in 10.0.17763.2061
Microsoft Windows Server version 2004: from 10.0.0 before 10.0.19041.1110 — fixed in 10.0.19041.1110
Microsoft Windows Server version 20H2: from 10.0.0 before 10.0.19042.1110 — fixed in 10.0.19042.1110

How to fix

Upgrade to a fixed version: Microsoft Windows 10 Version 1507 10.0.10240.19003; Microsoft Windows 10 1607 10.0.14393.4530; Microsoft Windows 10 10.0.17763.2061; Microsoft Windows 10 1909 10.0.18363.1679; Microsoft Windows 10 2004 10.0.19041.1110; Microsoft Windows 10 20H2 10.0.19042.1110; Microsoft Windows 10 21H1 10.0.19043.1110; Microsoft Windows 7 6.1.7601.25661; Microsoft Windows 7 Service Pack 1 6.1.7601.25661; Microsoft Windows 8.1 6.3.9600.20069; Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25661; Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21167. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-33765 or the next vulnerability affects your stack