Heap-Based Buffer Overflow in Windows Ancillary Function Driver
CVE-2026-21236

7.8HIGH

Key Information:

Vendor

Microsoft
Status
Windows 11 Version 26h1
Windows 11 Version 26h1
Windows 10 Version 1809
Windows Server 2019
Vendor
CVE Published:
10 February 2026

What is CVE-2026-21236?

The Windows Ancillary Function Driver for WinSock is susceptible to a heap-based buffer overflow issue. This vulnerability allows an authorized attacker to exploit the system and gain elevated privileges locally. Attackers leveraging this flaw may be able to perform actions that would otherwise be restricted, making it essential for users to apply the necessary patches to safeguard their systems.

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Affected Version(s)

Windows 10 Version 1607 32-bit Systems 10.0.14393.0 < 10.0.14393.8868

Windows 10 Version 1809 32-bit Systems 10.0.17763.0 < 10.0.17763.8389

Windows 10 Version 21H2 32-bit Systems 10.0.19044.0 < 10.0.19044.6937

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
7.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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