CVE-2026-40403

Name: CVE-2026-40403
Creator: NVD / NIST
Published: 2026-05-12T18:17:18.127+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 0.43%

Last modified Jun 17, 2026

CVE-2026-40403 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. Heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally.. EPSS estimates a 0.43% chance of exploitation in the next 30 days.

Description

Heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

0.43%

34.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-122

Affected Software

Vendor	Product	Versions
Microsoft	Windows 10 1607	< 10.0.14393.9140
Microsoft	Windows 10 1809	< 10.0.17763.8755
Microsoft	Windows 10 21h2	< 10.0.19044.7291
Microsoft	Windows 10 22h2	< 10.0.19045.7291
Microsoft	Windows 11 23h2	< 10.0.22631.7079
Microsoft	Windows 11 24h2	< 10.0.26100.8390
Microsoft	Windows 11 25h2	< 10.0.26200.8390
Microsoft	Windows 11 26h1	< 10.0.28000.2113
Microsoft	Windows Server 2012	All versions
Microsoft	Windows Server 2012	r2
Microsoft	Windows Server 2016	< 10.0.14393.9140
Microsoft	Windows Server 2019	< 10.0.17763.8755
Microsoft	Windows Server 2022	< 10.0.20348.5074
Microsoft	Windows Server 2022 23h2	< 10.0.25398.2330
Microsoft	Windows Server 2025	< 10.0.26100.32772

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40403Vendor Advisory

Timeline

Published: May 12, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-40403?

Heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally.

How severe is CVE-2026-40403?

CVE-2026-40403 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.43% probability of exploitation in the next 30 days.

How do I fix CVE-2026-40403?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-40403?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST