Critical severity · published Nov 10, 2021
CVE-2021-26443
Microsoft Virtual Machine Bus (VMBus) Remote Code Execution Vulnerability
9.0
CVSS
1.7%
EPSS
No
On KEV
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Attack vector
Adjacent
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)1.7% · higher than 77% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WI
Windows · Microsoft
20h2; 21h1; 1809; 1909 · source: NVD
WS
Windows Server 2016 · Microsoft
20h2; 2004 · source: NVD
WS
Windows Server 2019 · Microsoft
All versions, or not specified · source: NVD
WS
Windows Server 2022 · Microsoft
All versions, or not specified · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-26443
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-26443
msrc.microsoft.com
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26443
Patch
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26443
More from Windows
10.0
CVE-2020-1350
Microsoft Windows DNS Server Remote Code Execution Vulnerability
9.8
CVE-2025-59287
Windows Server Update Service (WSUS) Remote Code Execution Vulnerability
9.8
CVE-2019-0708
Microsoft Remote Desktop Services Remote Code Execution Vulnerability
9.8
CVE-2017-8543
Microsoft Windows Search Remote Code Execution Vulnerability
9.8
CVE-2008-4250
Microsoft Windows Buffer Overflow Vulnerability