CVE-2021-28476 — Windows Hyper-V Remote Code Execution Vulnerability

Executive Summary

None

Overview

9.9

CVSS CRITICAL

Critical

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Remote Code Execution

Released May 11 2021

Last Updated May 11 2021

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.38625 — 0.98448 percentile

NVD CVSS 9.9 CRITICAL — matches MSRC

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C

ATTACK VECTOR

Network

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Changed

CONFIDENTIALITY

High

INTEGRITY

High

AVAILABILITY

High

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 8.6

EPSS Score

0.38625

probability of exploitation in the next 30 days

0.98448 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

13 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 for x64-based Systems	`5003172 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1607 for x64-based Systems	`5003197 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1803 for x64-based Systems	`5003174 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1809 for x64-based Systems	`5003171 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1909 for x64-based Systems	`5003169 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 2004 for x64-based Systems	`5003173 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 7 for x64-based Systems Service Pack 1 5003233 (Monthly Rollup) 5003228 (Security Only) Critical Remote Code Execution 5001335 5001392 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.24597 6.1.7601.24598 Yes 5003233 5003228 Windows 8.1 for x64-based systems 5003209 (Monthly Rollup) 5003220 (Security Only) Critical Remote Code Execution 5001382 5001383 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.20017 Yes 5003209 5003220 Windows Server 2008 for x64-based Systems Service Pack 2 5003210 (Monthly Rollup) 5003225 (Security Only) Critical Remote Code Execution 5001389 5001332 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.21117 Yes 5003210 5003225 Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5003210 (Monthly Rollup) 5003225 (Security Only) Critical Remote Code Execution 5001389 5001332 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.21117 Yes 5003210 5003225 Windows Server 2008 R2 for x64-based Systems Service Pack 1 5003233 (Monthly Rollup) 5003228 (Security Only) Critical Remote Code Execution 5001335 5001392 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.24597 6.1.7601.24598 Yes 5003233 5003228 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5003233 (Monthly Rollup) 5003228 (Security Only) Critical Remote Code Execution 5001335 5001392 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.24597 6.1.7601.24598 Yes 5003233 5003228 Windows Server 2012 5003208 (Monthly Rollup) 5003203 (Security Only) Critical Remote Code Execution 5001387 5001383 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.2.9200.23347 Yes 5003208 5003203 Windows Server 2012 (Server Core installation) 5003208 (Monthly Rollup) 5003203 (Security Only) Critical Remote Code Execution 5001387 5001383 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.2.9200.23347 Yes 5003208 5003203 Windows Server 2012 R2 5003209 (Monthly Rollup) 5003220 (Security Only) Critical Remote Code Execution 5001382 5001383 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.20017 Yes 5003209 5003220 Windows Server 2012 R2 (Server Core installation) 5003209 (Monthly Rollup) 5003220 (Security Only) Critical Remote Code Execution 5001382 5001383 Base: 9.9 Temporal: 8.6 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.20017 Yes 5003209 5003220 Windows Server 2016	`5003197 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2016 (Server Core installation)	`5003197 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2019	`5003171 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2019 (Server Core installation)	`5003171 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server, version 1909 (Server Core installation)	`5003169 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server, version 2004 (Server Core installation)	`5003173 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server, version 20H2 (Server Core Installation)	`5003173 (Security Update)`	Critical	Remote Code Execution	Yes

Patches

6 patches

Article	Type	Restart
`5003172`	Security Update	Yes
`5003197`	Security Update	Yes
`5003174`	Security Update	Yes
`5003171`	Security Update	Yes
`5003169`	Security Update	Yes
`5003173`	Security Update	Yes

Exploits & PoC

6 public PoCs

Unverified third-party code

Public proof-of-concept repositories aggregated from PoC-in-GitHub. They are not reviewed and may be incomplete, non-functional, or malicious — inspect the code before running anything.

Repository	Stars	Published	Description
0vercl0k/CVE-2021-28476	226	2021-05-31	PoC for CVE-2021-28476 a guest-to-host "Hyper-V Remote Code Execution Vulnerability" in vmswitch.sys.
bluefrostsecurity/CVE-2021-28476	9	2021-06-02
australeo/CVE-2021-28476	5	2022-01-16	CVE-2021-28476: Hyper-V vmswitch.sys arbitrary pointer dereference from guest VM
LaCeeKa/CVE-2021-28476-tools-env	1	2021-08-15	tools for automate configure Ubuntu 20.04 enviroment for testing CVE-2021-28476.
dengyang123x/0vercl0k	1	2022-04-17	PoC for CVE-2021-28476 a guest-to-host "Hyper-V Remote Code Execution Vulnerability" in vmswitch.sys.
2273852279qqs/0vercl0k	0	2022-03-19	PoC for CVE-2021-28476 a guest-to-host "Hyper-V Remote Code Execution Vulnerability" in vmswitch.sys.

Detection Rules

No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.

Acknowledgments

Peleg Hadar ( @peleghd
Daniel Fernandez Kuehr
Leo Adrien ( @australeo

References

MSRC Advisory MITRE NVD