Windows
CVE-2026-21236
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessAuthenticated local access to system
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DeliveryCraft malicious WinSock function call
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ExploitTrigger heap buffer overflow in AFD.sys
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ExecutionWrite shellcode to heap memory
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ImpactExecute code with SYSTEM privileges
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Heap buffer bounds checking
MITRE ATT&CK
1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Authenticated local user account required. Windows Ancillary Function Driver (AFD.sys) must be loaded and accessible through WinSock API calls. Exploitation requires local code execution capability; cannot be performed remotely. |
| 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. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Windows Ancillary Function Driver for WinSock contains a heap buffer overflow vulnerability that enables authenticated local users to achieve privilege escalation on affected Windows 10 and Server 2012 systems. An attacker with valid user credentials can exploit this memory corruption flaw to execute arbitrary code with elevated privileges. No patch is currently available for this vulnerability.
Earlier versions of this analysis (1)
Heap-based buffer overflow 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. Enable ASLR, DEP/NX, and stack canaries where possible.
Affected Packages
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.
Technical ContextAI · show details
Classified as CWE-122 (Heap-based Buffer Overflow). Affects the Windows Ancillary component of Windows 10 1607. Heap-based buffer overflow 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
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
DescriptionCVE.org
Heap-based buffer overflow in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
Executive ViewAI
A privilege escalation vulnerability in Windows Ancillary Function Driver for WinSock (CVE-2026-21236) allows authenticated local users to gain elevated system access. This poses significant risk to organizational security as it could enable lateral movement, data exfiltration, and system compromise if exploited by insider threats or attackers who have already gained initial access to Windows systems.
Restrict local user account creation and administrative privileges; implement endpoint privilege management to limit elevation opportunities; deploy EDR/XDR tools to detect exploitation attempts; enforce strong access controls and monitor for suspicious driver-level activity; disable WinSock features not required for business operations; segment networks to limit lateral movement impact; establish audit logging for local privilege changes.
Threat Intelligence Overview
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.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.
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GitHub PoC
Exploit-DB