CVE-2026-40369: CVE-2026-40369: Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate priv…

What it is

Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

Exploitation evidence

First exploit evidence seen: 2026-05-13 (earliest date across the sources below).

Exploited in the wild

No source on this site lists in-the-wild exploitation yet (CISA KEV, VulnCheck KEV).

Public exploit code

GitHub proof-of-concept repositories

7 public repositories from 7 accounts, first seen 2026-05-13. Most starred: orinimron123/CVE-2026-40369-EXPLOIT (264 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: nomi-sec/PoC-in-GitHub.

How to fix it

Fixed versions

• microsoft windows 11 24h2: upgrade to 10.0.26100.8390 or later
• microsoft windows 11 25h2: upgrade to 10.0.26200.8390 or later
• microsoft windows 11 26h1: upgrade to 10.0.28000.2113 or later
• microsoft windows server 2025: upgrade to 10.0.26100.32772 or later

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40369 (Vendor Advisory)

Detection Generic guidance

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.