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Attack ChainAIDerived

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

  1. Access
    Authenticate as low-privilege local user
  2. Exploit
    Exploit improper access control in AFD.sys
  3. Execution
    Bypass privilege boundary checks
  4. Impact
    Achieve system-level code execution

Vulnerability Assessment

Weakness
CWE
CWE-284
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Access control enforcement
MITRE ATT&CK

1 technique across 1 tactic: Defense Evasion

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Local user account required with standard privileges. Windows Ancillary Function Driver (AFD.sys) enabled in default Windows network stack. No administrative privileges needed initially.
Impact

CVSS 7.8 (HIGH). Attack vector: Local. Complexity: Low. 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

Privilege escalation in the Windows Ancillary Function Driver for WinSock affects Windows 11 and Windows Server 2022/2019, allowing authenticated local users to gain elevated system privileges. The vulnerability stems from improper access control mechanisms and currently lacks a patch. An authenticated attacker with local access can exploit this to achieve full system compromise.

Earlier versions of this analysis (1)
v1 Mar 12, 2026 - 22:02 CVSS 7.8

Improper access control in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally. [CVSS 7.8 HIGH]

RemediationAI

Monitor vendor advisories for a patch.

Affected Packages

microsoft windows_10_version_1607_10_0_14393_8868 fix: Windows 10 Version 1607 for 32-bit Systems 10.0.14393.8868, Windows 10 Version 1607 for x64-based Systems 10.0.14393.8868
microsoft windows_10_version_1809_10_0_17763_8389 fix: Windows 10 Version 1809 for 32-bit Systems 10.0.17763.8389, Windows 10 Version 1809 for x64-based Systems 10.0.17763.8389
microsoft windows_10_version_21h2_10_0_19044_6937 fix: Windows 10 Version 21H2 for 32-bit Systems 10.0.19044.6937, Windows 10 Version 21H2 for ARM64-based Systems 10.0.19044.6937, Windows 10 Version 21H2 for x64-based Systems 10.0.19044.6937
microsoft windows_10_version_22h2_10_0_19045_6937 fix: Windows 10 Version 22H2 for 32-bit Systems 10.0.19045.6937, Windows 10 Version 22H2 for ARM64-based Systems 10.0.19045.6937, Windows 10 Version 22H2 for x64-based Systems 10.0.19045.6937
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_2012_6_2_9200_25923 fix: Windows Server 2012 6.2.9200.25923, Windows Server 2012 (Server Core installation) 6.2.9200.25923
microsoft windows_server_2012_r2_6_3_9600_23022 fix: Windows Server 2012 R2 6.3.9600.23022, Windows Server 2012 R2 (Server Core installation) 6.3.9600.23022
microsoft windows_server_2016_10_0_14393_8868 fix: Windows Server 2016 10.0.14393.8868, Windows Server 2016 (Server Core installation) 10.0.14393.8868
microsoft windows_server_2019_10_0_17763_8389 fix: Windows Server 2019 10.0.17763.8389, Windows Server 2019 (Server Core installation) 10.0.17763.8389
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 15 packages in microsoft

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

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Technical ContextAI · show details

Classified as CWE-284 (Improper Access Control). Affects the Windows Ancillary component of Windows 10 1607. Improper access control 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 7.8 HIGH
AV:L/AC:L/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
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

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

Executive ViewAI

Why It Matters

CVE-2026-21238 is a privilege escalation vulnerability in Windows that allows authorized local users to gain elevated system access. While currently unpatched, the vulnerability requires existing system access, limiting immediate risk; however, any compromise of standard user accounts could lead to full system control.

Business Impact: High
Compensating Controls

Restrict local administrative privileges and enforce principle of least privilege; disable or restrict access to Windows Ancillary Function Driver for WinSock if not required for operations; implement application whitelisting to prevent unauthorized privilege escalation tools; enhance endpoint detection and response (EDR) monitoring for privilege escalation techniques; segment networks to contain lateral movement from compromised standard user accounts; monitor for exploitation attempts in security logs and audit privileged account activities.

Threat Intelligence Overview

EPSS Score
0.0%
Top 94% 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
No
Human Impact
High

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Affected Products (CPE)CVE.org

cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x86:*
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_2012:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
+ 3 more

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Same weakness CWE-284 – Improper Access Control

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References

Advisories & patches
ADVISORY https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21238

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