CVE intelligence

CVE-2026-40405

Vulnerability intelligence

Published May 12, 2026Sources checked Nov 11, 2026

7.5HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-40405 and is rated High severity with a CVSS score of 7.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: May 12, 2026

Vendor remediation details

Install KB5087539. Install KB5087423. Install KB5089549. Install KB5089466. Install KB5089548.

Vendor-listed releases

10.0.26100.32860
10.0.26100.32772
10.0.26200.8457
10.0.26200.8390
10.0.26100.8457
10.0.26100.8390
10.0.28000.2113

CISA KEVNot listedBased on the latest collected catalog

EPSS1.1%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-40405?

Null pointer dereference in Windows TCP/IP allows an unauthorized attacker to deny service over a network.

Source: NVD