# CVE-2026-20860: Microsoft Windows Ancillary Function Driver type confusion privilege escalation

Source: https://junglewise.ai/threats/cve-2026-20860-microsoft-windows-ancillary-function-driver-type-confusion  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-01-13. Updated: 2026-07-30  
License: CC BY 4.0 with a link back

CVE-2026-20860 · Severity: high · CVSS 7.8 · Published 2026-01-13

A security vulnerability exists in the Windows component responsible for managing network socket connections. An attacker who already has basic access to a computer could exploit this flaw to gain full administrative control over the system. This could allow them to bypass security restrictions, access sensitive data, or install malicious software.

Technologies: [Microsoft Windows 11](https://junglewise.ai/threats/technologies/windows-11), [Microsoft Windows Server 2008 R2](https://junglewise.ai/threats/technologies/windows-server-2008-r2), [Microsoft Windows 10](https://junglewise.ai/threats/technologies/windows-10). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-20860 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20860 being exploited in the wild.

**How severe is CVE-2026-20860?** High severity, with a CVSS score of 7.8, published 13 January 2026.

**Which products and versions are affected?** Microsoft Windows 11 22H3, 23H2, 24H2, 25H2; Microsoft Windows Server 2008 R2 Service Pack 1; Microsoft Windows 10 1607, 1809, 21H2, 22H2.

**Is there a fix for CVE-2026-20860?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20860 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-20860?** Check whether you run Microsoft Windows 11, Microsoft Windows Server 2008 R2 or Microsoft Windows 10 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A type confusion vulnerability (CWE-843) exists in the Windows Ancillary Function Driver (afd.sys), which is the kernel-entry point for the Winsock interface. The flaw occurs when the driver improperly handles objects of incompatible types, leading to memory corruption or unintended execution flow in kernel mode. An attacker with low-privileged local access can exploit this by sending specially crafted I/O control (IOCTL) requests to the driver. Successful exploitation allows the attacker to execute code with SYSTEM privileges. Microsoft has released security updates to address this issue across various versions of Windows and Windows Server.

## Affected products

- Microsoft Windows 10 1607, 1809, 21H2, 22H2
- Microsoft Windows 11 22H3, 23H2, 24H2, 25H2
- Microsoft Windows Server 2008 R2 Service Pack 1

## Timeline

- 2026-01-13: disclosed
- 2026-01-13: advisory

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20860](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20860)

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- [Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.](https://junglewise.ai/threats/cve-2026-68820-microsoft-windows-ancillary-function-driver-for-winsock-use-after)
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- [Microsoft Windows Boot Loader security feature bypass](https://junglewise.ai/threats/cve-2026-58638-microsoft-windows-boot-loader-security-feature-bypass)
- [Microsoft Windows Client-Side Caching Service privilege escalation](https://junglewise.ai/threats/cve-2026-58637-microsoft-windows-client-side-caching-service-privilege)