CVE tracker / CVE-2026-40406

CVE-2026-40406

CVE-2026-40406 is the Windows TCP/IP Information Disclosure Vulnerability. Microsoft rates it Important, CVSS 7.5. It is not in CISA's Known Exploited Vulnerabilities catalog. Published May 12, 2026.

Risk summary

HighInformation Disclosure

7.5

CVSS v3 base

0.9%

EPSS: chance of exploitation in 30 days

High

Severity

Important

Microsoft's rating

Less Likely

Microsoft: exploitation

In CISA KEV

Microsoft describes it: “Use after free in Windows TCP/IP allows an unauthorized attacker to disclose information over a network.”

How to fix it

Microsoft lists 31 affected products and the update that fixes each:

KB5087420 · fixed build 10.0.22631.7079
Windows 11 Version 23H2 for ARM64-based Systems
KB5087470 · fixed build 6.2.9200.26079
Windows Server 2012 (Server Core installation), Windows Server 2012
KB5087471 · fixed build 6.3.9600.23181
Windows Server 2012 R2 (Server Core installation), Windows Server 2012 R2
KB5087537 · fixed build 10.0.14393.9140
Windows Server 2016 (Server Core installation), Windows Server 2016, Windows 10 Version 1607 for x64-based Systems, Windows 10 Version 1607 for 32-bit Systems
KB5087538 · fixed build 10.0.17763.8755
Windows Server 2019 (Server Core installation), Windows Server 2019, Windows 10 Version 1809 for x64-based Systems, Windows 10 Version 1809 for 32-bit Systems
KB5087539 · fixed build 10.0.26100.32860
Windows Server 2025, Windows Server 2025 (Server Core installation)
KB5087541 · fixed build 10.0.25398.2330
Windows Server 2022, 23H2 Edition (Server Core installation)
KB5087544 · fixed build 10.0.19044.7291
Windows 10 Version 21H2 for x64-based Systems, Windows 10 Version 21H2 for ARM64-based Systems, Windows 10 Version 21H2 for 32-bit Systems
KB5087545 · fixed build 10.0.20348.5139
Windows Server 2022 (Server Core installation), Windows Server 2022
KB5089548 · fixed build 10.0.28000.2113
Windows 11 Version 26H1 for ARM64-based Systems, Windows 11 version 26H1 for x64-based Systems
KB5089549 · fixed build 10.0.26100.8457, 10.0.26200.8457
Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 25H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems
KB5093998 · fixed build 10.0.22631.7219
Windows 11 Version 23H2 for x64-based Systems
KB5094127 · fixed build 10.0.19045.7417
Windows 10 Version 22H2 for 32-bit Systems, Windows 10 Version 22H2 for ARM64-based Systems, Windows 10 Version 22H2 for x64-based Systems

What Microsoft changed

May 12, 2026: Information published.

Details

Weakness: CWE-416: Use After Free
Publicly disclosed (Microsoft): No
Exploited (Microsoft): No
Known exploited (CISA KEV): Not listed
Published: May 12, 2026
Last revised: May 12, 2026

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References

Microsoft Security Update Guide NVD CVE record CWE

From Microsoft, CISA, NVD and FIRST data; the Microsoft details were read when this page was opened. Check the references above before you act.