PT-2026-40217 · Microsoft · Windows Win32K+1

Published 2026-05-12 · Updated 2026-05-12 · CVE-2026-40403

Positive Technologies (AI Summary)

CVSS v3.1

8.8

High

Base vector

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

Name of the Vulnerable Software and Affected Versions Windows Win32K - GRFX (affected versions not specified)

Description A heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally. This issue can potentially be used to escape a virtual machine sandbox.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

RCE

Heap Based Buffer Overflow

Weakness Enumeration

CWE-122

Related Identifiers

BDU:2026-06859

CVE-2026-40403

Affected Products

Windows

Windows Win32K

References · 6

• https://nvd.nist.gov/vuln/detail/CVE-2026-40403 · Security Note
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40403 · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-06859 · Security Note
• http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-40403 · Security Note
• https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2026-40403 · Vendor Advisory
• https://twitter.com/windowsforum/status/2054320684260593923 · Twitter Post