CVE-2026-21238

highpriority · track · 1EPSS 0.034 · 89 %ileDEEUJPNLRUUS

grimoire priorityP2 · Scheduled

Exploitable?

—

no known exploitation

Likely / severe?

3.38% (89th) EPSS

CVSS 7.8 · high

Is it mine?

193 products

Check your exposure

Who says so?

7 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-26

Improper access control in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedWindows 10 Version 1607 for 32-bit Systemsmsrc_csaf
10.0.14393.8868:Security Update:https://support.microsoft.com/help/5075999
https://support.microsoft.com/help/5075999
FixedWindows 10 Version 1607 for x64-based Systemsmsrc_csaf
10.0.14393.8868:Security Update:https://support.microsoft.com/help/5075999
https://support.microsoft.com/help/5075999
FixedWindows 10 Version 1809 for 32-bit Systemsmsrc_csaf
10.0.17763.8389:Security Update:https://support.microsoft.com/help/5075904
https://support.microsoft.com/help/5075904
FixedWindows 10 Version 1809 for x64-based Systemsmsrc_csaf
10.0.17763.8389:Security Update:https://support.microsoft.com/help/5075904
https://support.microsoft.com/help/5075904
FixedWindows 10 Version 21H2 for 32-bit Systemsmsrc_csaf
10.0.19044.6937:Security Update:https://support.microsoft.com/help/5075912
https://support.microsoft.com/help/5075912
FixedWindows 10 Version 21H2 for ARM64-based Systemsmsrc_csaf
10.0.19044.6937:Security Update:https://support.microsoft.com/help/5075912
https://support.microsoft.com/help/5075912
FixedWindows 10 Version 21H2 for x64-based Systemsmsrc_csaf
10.0.19044.6937:Security Update:https://support.microsoft.com/help/5075912
https://support.microsoft.com/help/5075912
FixedWindows 10 Version 22H2 for 32-bit Systemsmsrc_csaf
10.0.19045.6937:Security Update:https://support.microsoft.com/help/5075912
https://support.microsoft.com/help/5075912
FixedWindows 10 Version 22H2 for ARM64-based Systemsmsrc_csaf
10.0.19045.6937:Security Update:https://support.microsoft.com/help/5075912
https://support.microsoft.com/help/5075912
FixedWindows 10 Version 22H2 for x64-based Systemsmsrc_csaf
10.0.19045.6937:Security Update:https://support.microsoft.com/help/5075912
https://support.microsoft.com/help/5075912
FixedWindows 11 Version 23H2 for ARM64-based Systemsmsrc_csaf
10.0.22631.6649:Security Update:https://support.microsoft.com/help/5075941
https://support.microsoft.com/help/5075941
FixedWindows 11 Version 23H2 for x64-based Systemsmsrc_csaf
10.0.22631.6649:Security Update:https://support.microsoft.com/help/5075941
https://support.microsoft.com/help/5075941
FixedWindows 11 Version 24H2 for ARM64-based Systemsmsrc_csaf
10.0.26100.7840:Security Update:https://support.microsoft.com/help/5077181
https://support.microsoft.com/help/5077181
FixedWindows 11 Version 24H2 for x64-based Systemsmsrc_csaf
10.0.26100.7840:Security Update:https://support.microsoft.com/help/5077181
https://support.microsoft.com/help/5077181
FixedWindows 11 Version 25H2 for ARM64-based Systemsmsrc_csaf
10.0.26200.7840:Security Update:https://support.microsoft.com/help/5077181
https://support.microsoft.com/help/5077181
FixedWindows 11 Version 25H2 for x64-based Systemsmsrc_csaf
10.0.26200.7840:Security Update:https://support.microsoft.com/help/5077181
https://support.microsoft.com/help/5077181
FixedWindows 11 Version 26H1 for ARM64-based Systemsmsrc_csaf
10.0.28000.1575:Security Update:https://support.microsoft.com/help/5077179
https://support.microsoft.com/help/5077179
FixedWindows 11 version 26H1 for x64-based Systemsmsrc_csaf
10.0.28000.1575:Security Update:https://support.microsoft.com/help/5077179
https://support.microsoft.com/help/5077179
FixedWindows Server 2012msrc_csaf
6.2.9200.25923:Monthly Rollup:https://support.microsoft.com/help/5075971
https://support.microsoft.com/help/5075971
FixedWindows Server 2012 (Server Core installation)msrc_csaf
6.2.9200.25923:Monthly Rollup:https://support.microsoft.com/help/5075971
https://support.microsoft.com/help/5075971
FixedWindows Server 2012 R2msrc_csaf
6.3.9600.23022:Monthly Rollup:https://support.microsoft.com/help/5075970
https://support.microsoft.com/help/5075970
FixedWindows Server 2012 R2 (Server Core installation)msrc_csaf
6.3.9600.23022:Monthly Rollup:https://support.microsoft.com/help/5075970
https://support.microsoft.com/help/5075970
FixedWindows Server 2016msrc_csaf
10.0.14393.8868:Security Update:https://support.microsoft.com/help/5075999
https://support.microsoft.com/help/5075999
FixedWindows Server 2016 (Server Core installation)msrc_csaf
10.0.14393.8868:Security Update:https://support.microsoft.com/help/5075999
https://support.microsoft.com/help/5075999
FixedWindows Server 2019msrc_csaf
10.0.17763.8389:Security Update:https://support.microsoft.com/help/5075904
https://support.microsoft.com/help/5075904
FixedWindows Server 2019 (Server Core installation)msrc_csaf
10.0.17763.8389:Security Update:https://support.microsoft.com/help/5075904
https://support.microsoft.com/help/5075904
FixedWindows Server 2022msrc_csaf
10.0.20348.4773:Security Update:https://support.microsoft.com/help/5075906
https://support.microsoft.com/help/5075906
FixedWindows Server 2022 (Server Core installation)msrc_csaf
10.0.20348.4773:Security Update:https://support.microsoft.com/help/5075906
https://support.microsoft.com/help/5075906
FixedWindows Server 2022, 23H2 Edition (Server Core installation)msrc_csaf
10.0.25398.2149:Security Update:https://support.microsoft.com/help/5075897
https://support.microsoft.com/help/5075897
FixedWindows Server 2025msrc_csaf
10.0.26100.32370:Security Update:https://support.microsoft.com/help/5075899
https://support.microsoft.com/help/5075899
FixedWindows Server 2025 (Server Core installation)msrc_csaf
10.0.26100.32370:Security Update:https://support.microsoft.com/help/5075899
https://support.microsoft.com/help/5075899

cvss

Technical severity, 0–10. One row per scoring source.

7.8

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.17.8highAV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · ENISA EU

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsecondary · secure@microsoft.com USexploitability 1.8 · impact 5.9

v3.17.1highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · NCSC-NL NL

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · Microsoft Security Response Center US

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-284USCWE-284USCWE-284USCWE-284US

affected products (193)

Products and version ranges known to be affected.

Hitachi Storageall versionscert_bundDEcpe:/h:hitachi:storage:-
Microsoft Exchange Server 2016 Cumulative Update 23all versionscert_bundDEcpe:/a:microsoft:exchange:server_2016_cumulative_update_23
Microsoft Exchange Server 2019 Cumulative Update 14all versionscert_bundDEcpe:/a:microsoft:exchange:server_2019_cumulative_update_14
Microsoft Exchange Server 2019 Cumulative Update 15all versionscert_bundDEcpe:/a:microsoft:exchange:server_2019_cumulative_update_15
Microsoft Windows 10 Version 1607all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1607
Microsoft Windows 10 Version 1809all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1809
Microsoft Windows 10 Version 21H2all versionscert_bundDEcpe:/o:microsoft:windows_10:version_21h2
Microsoft Windows 10 Version 22H2all versionscert_bundDEcpe:/o:microsoft:windows_10:version_22h2
Microsoft Windows 11 Version 23H2all versionscert_bundDEcpe:/o:microsoft:windows_11:version_23h2
Microsoft Windows 11 Version 24H2all versionscert_bundDEcpe:/o:microsoft:windows_11:version_24h2
Microsoft Windows 11 Version 25H2all versionscert_bundDEcpe:/o:microsoft:windows_11:version_25h2
Microsoft Windows 11 Version 26H1all versionscert_bundDEcpe:/o:microsoft:windows_11:version_26h1
Microsoft Windows 11 version 26H1all versionscert_bundDE
Microsoft Windows App for Macall versionscert_bundDEcpe:/o:microsoft:windows:app_for_mac
Microsoft Windows Server 2012all versionscert_bundDEcpe:/o:microsoft:windows_server_2012:-
Microsoft Windows Server 2012 R2all versionscert_bundDEcpe:/o:microsoft:windows_server_2012_r2:-
Microsoft Windows Server 2016all versionscert_bundDEcpe:/o:microsoft:windows_server_2016:-
Microsoft Windows Server 2019all versionscert_bundDEcpe:/o:microsoft:windows_server_2019:-
Microsoft Windows Server 2022all versionscert_bundDEcpe:/o:microsoft:windows_server_2022:-
Microsoft Windows Server 2022 23H2 Editionall versionscert_bundDEcpe:/o:microsoft:windows_server_2022:23h2_edition

showing 20 of 193

advisories (4)

Vendor and ecosystem advisories describing this.

NCSC-2026-0053Kwetsbaarheden verholpen in Microsoft WindowsNL2026-02-10csaf · ncsc_nlNL
Microsoft heeft kwetsbaarheden verholpen in Windows.
WID-SEC-W-2026-0369Microsoft Windows: Mehrere SchwachstellenDeutsch2026-02-10csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Microsoft Windows-Produkten ausnutzen, um Administratorrechte zu erlangen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Spoofing-Angriffe zu starten, Daten zu manipulieren, vertrauliche Informationen offenzulegen und einen Denial-of-Service-Zustand zu verursachen.
msrc_CVE-2026-21238Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability2026-02-10csaf · msrc_csafUS
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle
JVNDB-2026-009406JVN iPedia advisory JVNDB-2026-0094062026-03-31vendor · jvndbJP

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund ncsc_nl msrc_csaf jvndb NVD CVE.org MITRE

published 2026-02-10modified 2026-06-17

references (3)

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan