PT-2026-47890 · Microsoft · Windows Ancillary Function Driver For Winsock+1

CVE-2026-42911 · Published 2026-06-09 · Updated 2026-06-21

Positive Technologies (AI Summary)

CVSS v3.1

7.0

High

Base vector

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

Name of the Vulnerable Software and Affected Versions Windows Ancillary Function Driver for WinSock versions prior to June 2026 security updates

Description A use-after-free issue exists in the kernel-mode networking subsystem of the Ancillary Function Driver for WinSock (afd.sys). This occurs when the kernel dereferences a stale pointer and operates on memory controlled by an attacker after a kernel object has been freed and reclaimed. This memory corruption can be leveraged to achieve arbitrary kernel code execution, allowing a local authorized attacker to elevate privileges from a low-privileged user account to SYSTEM without requiring user interaction.

Recommendations Update to the June 2026 security updates.

Fix

DoS

LPE

Use After Free

Weakness Enumeration

CWE-416

Related Identifiers

BDU:2026-08207

CVE-2026-42911

Affected Products

Windows

Windows Ancillary Function Driver For Winsock

References · 9

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42911 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-42911 · Security Note
• https://bdu.fstec.ru/vul/2026-08207 · Security Note
• https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2026-42911 · Vendor Advisory
• http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-42911 · Security Note
• https://t.me/cveNotify/167127 · Telegram Post
• https://twitter.com/OSdev_/status/2068637207293051043 · Twitter Post
• https://twitter.com/windowsforum/status/2064536513891721357 · Twitter Post
• https://twitter.com/OSdev_/status/2067237692723560458 · Twitter Post