What is CVE-2026-45657?

CVE-2026-45657 is a critical-severity vulnerability in Microsoft Windows_11_23h2, classified under Heap-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-06-09.

How severe is CVE-2026-45657?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Microsoft Windows_11_23h2

CVE-2026-45657

Use after free in Windows Kernel allows an unauthorized attacker to execute code over a network.

Vulnerability class: Buffer Overflow

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Microsoft Windows_11_23h2
Microsoft Windows_11_24h2
Microsoft Windows_11_25h2
Microsoft Windows_11_26h1
Microsoft Windows_server_2022
Microsoft Windows_server_2025

Weakness classification (CWE)

CWE-122 — Heap-based Buffer Overflow
CWE-416 — Use After Free

References

secure@microsoft.com (Vendor Advisory)

Frequently asked questions

What is CVE-2026-45657?: CVE-2026-45657 is a critical-severity vulnerability in Microsoft Windows_11_23h2, classified under Heap-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-06-09.
How severe is CVE-2026-45657?: Critical severity. CVSS v3 base score is 9.8 out of 10.