CVE-2021-28476 [Critical] | RCE in Windows 10

CVE-2021-28476 is rated High Risk (78.9/100): CVSS Critical severity, with high exploitation likelihood (EPSS 55.15%, 98th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +6.36% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-04	48.79%	55.15%	+6.36%
2	2026-05-22	55.15%	48.79%	-6.36%
3	2026-04-24	—	55.15%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-04

48.79%

55.15%

+6.36%

2026-05-22

55.15%

48.79%

-6.36%

2026-04-24

—

55.15%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
9.9	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.1	6.0	[email protected]
9.9	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.1	6.0	[email protected]
6.5	2.0	MEDIUM	`AV:N/AC:L/Au:S/C:P/I:P/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:S) A single authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	8.0	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

9.9

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.1

6.0

[email protected]

9.9

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.1

6.0

[email protected]

6.5

2.0

MEDIUM

AV:N/AC:L/Au:S/C:P/I:P/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:S): A single authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

8.0

6.4

[email protected]

Affected software / configurations for CVE-2021-28476

Vendor	Product	Version	Raw CPE
microsoft	windows_10	—	cpe:2.3:o:microsoft:windows_10:-::::::x64:
microsoft	windows_10	20h2	cpe:2.3:o:microsoft:windows_10:20h2::::::x64:
microsoft	windows_10	1607	cpe:2.3:o:microsoft:windows_10:1607::::::x64:
microsoft	windows_10	1803	cpe:2.3:o:microsoft:windows_10:1803::::::x64:
microsoft	windows_10	1809	cpe:2.3:o:microsoft:windows_10:1809::::::x64:
microsoft	windows_10	1909	cpe:2.3:o:microsoft:windows_10:1909::::::x64:
microsoft	windows_10	2004	cpe:2.3:o:microsoft:windows_10:2004::::::x64:
microsoft	windows_7	—	cpe:2.3:o:microsoft:windows_7:-:sp1:::::x64:*
microsoft	windows_8.1	—	cpe:2.3:o:microsoft:windows_8.1:-::::::x64:
microsoft	windows_server_2008	—	cpe:2.3:o:microsoft:windows_server_2008:-:sp2:::::x64:*
microsoft	windows_server_2008	r2	cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:::::x64:*
microsoft	windows_server_2012	—	cpe:2.3:o:microsoft:windows_server_2012:-:::::::*
microsoft	windows_server_2012	r2	cpe:2.3:o:microsoft:windows_server_2012:r2:::::::*
microsoft	windows_server_2016	—	cpe:2.3:o:microsoft:windows_server_2016:-:::::::*
microsoft	windows_server_2016	20h2	cpe:2.3:o:microsoft:windows_server_2016:20h2:::::::*
microsoft	windows_server_2016	1909	cpe:2.3:o:microsoft:windows_server_2016:1909:::::::*
microsoft	windows_server_2016	2004	cpe:2.3:o:microsoft:windows_server_2016:2004:::::::*
microsoft	windows_server_2019	—	cpe:2.3:o:microsoft:windows_server_2019:-:::::::*

References for CVE-2021-28476

URL	Tags
http://packetstormsecurity.com/files/163497/Microsoft-Hyper-V-vmswitch.sys-Proof-Of-Concept.html	Third Party Advisory VDB Entry
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28476	Patch Vendor Advisory

URL

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

Exploit prediction scoring system (EPSS) score for CVE-2021-28476

Common vulnerability scoring system (CVSS) metrics for CVE-2021-28476

Weakness enumeration for CVE-2021-28476

Affected software / configurations for CVE-2021-28476

References for CVE-2021-28476