CVE-2021-33771 [Exploited] | Microsoft WINDOWS 10 1507

CVE-2021-33771 is rated Critical Active Threat (88.4/100): CVSS High severity, with high exploitation likelihood (EPSS 6.20%, 93th percentile). CISA KEV confirms active exploitation (added 2021-11-03) affecting Microsoft / Windows. Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	6.44%	6.20%	-0.24%
2	2026-06-04	6.52%	6.44%	-0.08%
3	2026-05-22	—	6.52%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

6.44%

6.20%

-0.24%

2026-06-04

6.52%

6.44%

-0.08%

2026-05-22

—

6.52%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.8	3.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. 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:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. 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.	1.8	5.9	[email protected]
7.8	3.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. 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:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. 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.	1.8	5.9	[email protected]
7.2	2.0	HIGH	`AV:L/AC:L/Au:N/C:C/I:C/A:C` Click to expand Access vector (AV:L) Requires local access to the target system. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:C) Complete confidentiality impact. Integrity impact (I:C) Complete integrity impact. Availability impact (A:C) Complete availability impact.	3.9	10.0	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.8

3.1

HIGH

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
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:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
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.

1.8

5.9

[email protected]

7.8

3.1

HIGH

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
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:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
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.

1.8

5.9

[email protected]

7.2

2.0

HIGH

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

Access vector (AV:L): Requires local access to the target system.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:C): Complete confidentiality impact.
Integrity impact (I:C): Complete integrity impact.
Availability impact (A:C): Complete availability impact.

3.9

10.0

[email protected]

Affected software / configurations for CVE-2021-33771

Vendor	Product	Version	Raw CPE
microsoft	windows_10_1507	< 10.0.10240.19003	cpe:2.3:o:microsoft:windows_10_1507::::::::
microsoft	windows_10_1607	< 10.0.14393.4530	cpe:2.3:o:microsoft:windows_10_1607::::::::
microsoft	windows_10_1809	< 10.0.17763.2061	cpe:2.3:o:microsoft:windows_10_1809::::::::
microsoft	windows_10_1909	< 10.0.18363.1679	cpe:2.3:o:microsoft:windows_10_1909::::::::
microsoft	windows_10_2004	< 10.0.19041.1110	cpe:2.3:o:microsoft:windows_10_2004::::::::
microsoft	windows_10_20h2	< 10.0.19042.1110	cpe:2.3:o:microsoft:windows_10_20h2::::::::
microsoft	windows_10_21h1	< 10.0.19043.1110	cpe:2.3:o:microsoft:windows_10_21h1::::::::
microsoft	windows_8.1	—	cpe:2.3:o:microsoft:windows_8.1:-:::::::*
microsoft	windows_rt_8.1	—	cpe:2.3:o:microsoft:windows_rt_8.1:-:::::::*
microsoft	windows_server_2004	< 10.0.19041.1110	cpe:2.3:o:microsoft:windows_server_2004::::::::
microsoft	windows_server_2008	—	cpe:2.3:o:microsoft:windows_server_2008:-:sp1:::::x64:*
microsoft	windows_server_2008	—	cpe:2.3:o:microsoft:windows_server_2008:-:sp2::::::
microsoft	windows_server_2012	—	cpe:2.3:o:microsoft:windows_server_2012:-:r2::::::
microsoft	windows_server_2016	< 10.0.14393.4530	cpe:2.3:o:microsoft:windows_server_2016::::::::
microsoft	windows_server_2019	< 10.0.17763.2061	cpe:2.3:o:microsoft:windows_server_2019::::::::
microsoft	windows_server_20h2	< 10.0.19042.1110	cpe:2.3:o:microsoft:windows_server_20h2::::::::

References for CVE-2021-33771

URL	Tags
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33771	Patch Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33771	US Government Resource

URL

CVE-2021-33771 | Windows Kernel Elevation of Privilege Vulnerability

CISA KEV Record for CVE-2021-33771

Exploit prediction scoring system (EPSS) score for CVE-2021-33771

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33771

Weakness enumeration for CVE-2021-33771

Affected software / configurations for CVE-2021-33771

References for CVE-2021-33771