What is the CVSS score of CVE-2026-21241?

CVE-2026-21241 has a CVSS 3.1 base score of 7.0 (High). CVSS vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

How to fix or mitigate CVE-2026-21241?

Within 24 hours: Inventory all Windows systems and identify those with the vulnerable WinSock driver; disable non-essential WinSock Auxiliary Function Driver services where operationally feasible. Within 7 days: Implement network segmentation to restrict local access for non-administrative users; audit and enforce principle of least privilege for all user accounts. Within 30 days: Monitor vendor advisories for patch release; conduct privilege access management (PAM) review to minimize accounts with local logon rights; consider compensating controls such as application whitelisting to restrict driver loading.

Windows CVE-2026-21241

HIGH

Use After Free (CWE-416)

2026-02-10 secure@microsoft.com

Windows Use After Free Microsoft Windows 11 23h2 Windows 11 24h2 Windows 11 25h2 Windows Server 2022 Windows Server 2022 23h2 Windows Server 2025

7.0

CVSS 3.1 · NVD

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Authenticate with local user account
Exploit

Trigger use-after-free in WinSock AuxFD
Execution

Corrupt kernel memory structures
Impact

Execute arbitrary code in kernel context

Vulnerability Assessment

Weakness	CWE CWE-416 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Memory lifecycle management MITRE ATT&CK 2 techniques across 2 tactics: Execution, Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Exploitation Conditions	Requires local authenticated user account (PR:L) on Windows system with WinSock Ancillary Function Driver loaded. Specific trigger conditions and race conditions must be met (AC:H). Typical default Windows installations with standard network stack.
Impact	CVSS 7.0 (HIGH). Attack vector: Local. Complexity: High. Privileges required: Low. User interaction: None. Exploitable via local access.
Exploit ScenarioDerived	An attacker could exploit this vulnerability to compromise the affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Windows Ancillary Function Driver for WinSock in Windows 11 23h2 and Windows Server 2022 23h2 contains a use-after-free vulnerability that allows authenticated local users to achieve privilege escalation. An attacker with local access and valid credentials can trigger the memory safety flaw to gain elevated system privileges. No patch is currently available for this HIGH severity vulnerability.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 22:02 CVSS 7.0

Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally. [CVSS 7.0 HIGH]

RemediationAI

Monitor vendor advisories for a patch.

Affected Packages

microsoft windows_11_version_23h2_10_0_22631_6649 fix: Windows 11 Version 23H2 for ARM64-based Systems 10.0.22631.6649, Windows 11 Version 23H2 for x64-based Systems 10.0.22631.6649

microsoft windows_11_version_24h2_10_0_26100_7840 fix: Windows 11 Version 24H2 for ARM64-based Systems 10.0.26100.7840, Windows 11 Version 24H2 for x64-based Systems 10.0.26100.7840

microsoft windows_11_version_25h2_10_0_26200_7840 fix: Windows 11 Version 25H2 for ARM64-based Systems 10.0.26200.7840, Windows 11 Version 25H2 for x64-based Systems 10.0.26200.7840

microsoft windows_11_version_26h1_10_0_28000_1575 fix: Windows 11 Version 26H1 for ARM64-based Systems 10.0.28000.1575, Windows 11 version 26H1 for x64-based Systems 10.0.28000.1575

microsoft windows_server_2022_10_0_20348_4773 fix: Windows Server 2022 10.0.20348.4773, Windows Server 2022 (Server Core installation) 10.0.20348.4773

microsoft windows_server_2022_23h2_edition_10_0_25398_2149 fix: Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149

microsoft windows_server_2025_10_0_26100_32370 fix: Windows Server 2025 10.0.26100.32370, Windows Server 2025 (Server Core installation) 10.0.26100.32370

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 7 packages in microsoft

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Classified as CWE-416 (Use After Free). Affects the Windows Ancillary component of Windows 11 23H2. Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.0 HIGH

AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionCVE.org

Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Executive ViewAI

Why It Matters

A high-severity privilege escalation vulnerability in Windows Ancillary Function Driver for WinSock (CVE-2026-21241) allows authorized local users to gain elevated system privileges. Since no patch is currently available, all Windows systems running affected versions face elevated risk and require immediate compensating controls to prevent exploitation.

Business Impact: High

Compensating Controls

Disable or restrict access to the WinSock Auxiliary Function Driver if not required for business operations; implement application whitelisting to prevent unauthorized driver loading; enforce strict local administrative account controls and multi-factor authentication for privileged access; apply AppLocker or Device Guard policies to restrict code execution; increase monitoring and alerting on privilege escalation events; segment networks to limit lateral movement post-exploitation; monitor vendor security bulletins closely for patch availability.

Threat Intelligence Overview

EPSS Score

0.0%

Top 97% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Small

Automatable· derived

Human Impact

High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +35

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Use After Free HIGH

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Affected Products (CPE)CVE.org

cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*

cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*

cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*

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References

Advisories & patches

ADVISORY https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21241

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