What is the CVSS score of CVE-2026-42911?

CVE-2026-42911 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: 0.1%.

Which versions of Windows Ancillary Function Driver are affected by CVE-2026-42911?

CVE-2026-42911 is a privilege escalation flaw in the Windows WinSock kernel driver (afd.sys) that allows any authenticated local user to gain SYSTEM access, effectively granting administrator control…. A patch is available.

How to fix or mitigate CVE-2026-42911?

Within 24 hours: Audit and inventory Windows systems, prioritizing those with shared or multi-user access. Within 7 days: Deploy Microsoft's afd.sys security update to all Windows systems via Windows Update or enterprise deployment tools (consult Microsoft Security Update Guide for exact patch versions matching your Windows SKUs). Within 30 days: Verify 100% patch deployment coverage and deploy endpoint detection signatures to alert on afd.sys exploitation attempts.

Windows Ancillary Function Driver CVE-2026-42911

EUVD-2026-35723 HIGH

Use After Free (CWE-416)

2026-06-09 secure@microsoft.com

GHSA-cm32-vwv6-jwp3

Microsoft Use After Free Memory Corruption Denial Of Service

7.0

CVSS 3.1 · NVD

Temporal: 6.1

Severity by source

NVD PRIMARY

7.0 HIGH

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

CIRCL (temporal)

6.1 MEDIUM

cvss

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Local

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Jun 09, 2026 - 18:36 vuln.today

CVE Published

Jun 09, 2026 - 17:17 nvd

HIGH 7.0

DescriptionNVD

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

AnalysisAI

Local privilege escalation in the Windows Ancillary Function Driver for WinSock (afd.sys) allows an authenticated low-privileged user to elevate to SYSTEM via a use-after-free condition. The flaw affects Microsoft Windows installations using the standard WinSock kernel driver and has a vendor-released patch available through Microsoft's security update guide. No public exploit has been identified at time of analysis, though afd.sys has historically been a frequent target for elevation-of-privilege exploitation.

Technical ContextAI

The Ancillary Function Driver for WinSock (afd.sys) is a kernel-mode driver that provides the underlying support for Windows Sockets (WinSock) API calls from user-mode applications, bridging socket operations into the TCP/IP stack. CWE-416 (Use After Free) indicates the driver references kernel memory after it has been freed, typically when concurrent IOCTL requests or asynchronous I/O operations manipulate object lifetimes incorrectly. Successful manipulation of the dangling pointer permits an attacker to corrupt kernel memory structures, ultimately hijacking execution flow within ring 0. This driver class has been repeatedly abused in past Windows LPE chains because it is reachable from any process with a socket handle.

RemediationAI

Apply the vendor-released patch from Microsoft via the standard Windows Update channel or the security update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42911; the exact KB and build numbers should be confirmed against the MSRC advisory for the specific Windows SKU in use. As compensating controls until patching is complete, enforce least-privilege user accounts to limit which local actors can reach afd.sys, deploy attack-surface-reduction rules and EDR detections targeting suspicious afd.sys IOCTL abuse or token-stealing patterns, and prioritize patching endpoints reachable by untrusted code (developer workstations, terminal servers, multi-user systems). These compensating measures reduce - but do not eliminate - exposure because any local code execution path can attempt the race, and additional reference: https://vuldb.com/vuln/369611.