Description
Null pointer dereference in Windows TCP/IP allows an unauthorized attacker to deny service over a network.
Published: 2026-05-12
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

A null pointer dereference in the Windows TCP/IP stack can be triggered remotely over a network, causing the system to crash or become unresponsive. The flaw allows an attacker to cause a denial of service without needing privileged access. This vulnerability falls under CWE‑476, which signifies an attempt to dereference a null pointer.

Affected Systems

Microsoft Windows 11 24H2, Windows 11 25H2, Windows 11 26H1, Windows Server 2025, and the Server Core installation of Windows Server 2025. The affected builds include both ARM64 (for Windows 11 24H2 and 25H2) and x64 (for Windows 11 26H1) architectures.

Risk and Exploitability

The CVSS score of 7.5 indicates a high severity level for availability impact. The EPSS score is not available, but the lack of an entry in the CISA KEV catalog suggests no public exploitation has been confirmed. Attackers could exploit the vulnerability by sending crafted TCP/IP packets from a remote network, as the flaw does not require authentication. Successful exploitation would result in a service interruption for the affected host.

Generated by OpenCVE AI on May 12, 2026 at 19:23 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Check for and install any Microsoft security updates that address CVE‑2026‑40405.
  • Configure network devices or the Windows firewall to limit inbound TCP/IP traffic from untrusted sources that could trigger the fault.
  • Monitor system performance and log files for signs of denial‑of‑service activity and report incidents to Microsoft Security Response Center.

Generated by OpenCVE AI on May 12, 2026 at 19:23 UTC.

Tracking

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Advisories

No advisories yet.

History

Fri, 15 May 2026 15:30:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:x64:*

Wed, 13 May 2026 10:00:00 +0000

Type Values Removed Values Added
First Time appeared Microsoft windows 11 24h2
Microsoft windows 11 25h2
Microsoft windows 11 26h1
Microsoft windows Server 2025 (server Core Installation)
Vendors & Products Microsoft windows 11 24h2
Microsoft windows 11 25h2
Microsoft windows 11 26h1
Microsoft windows Server 2025 (server Core Installation)

Tue, 12 May 2026 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 12 May 2026 17:30:00 +0000

Type Values Removed Values Added
Description Null pointer dereference in Windows TCP/IP allows an unauthorized attacker to deny service over a network.
Title Windows TCP/IP Denial of Service Vulnerability
First Time appeared Microsoft
Microsoft windows 11 24h2
Microsoft windows 11 25h2
Microsoft windows 11 26h1
Microsoft windows Server 2025
Weaknesses CWE-476
CPEs cpe:2.3:o:microsoft:windows_11_24H2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_25H2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_26H1:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*
Vendors & Products Microsoft
Microsoft windows 11 24h2
Microsoft windows 11 25h2
Microsoft windows 11 26h1
Microsoft windows Server 2025
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C'}

Subscriptions

Microsoft Windows 11 24h2 Windows 11 24h2 Windows 11 25h2 Windows 11 25h2 Windows 11 26h1 Windows 11 26h1 Windows Server 2025 Windows Server 2025 (server Core Installation)
cve-icon MITRE

Status: PUBLISHED

Assigner: microsoft

Published:

Updated: 2026-06-09T18:08:25.054Z

Reserved: 2026-04-13T00:27:50.798Z

Link: CVE-2026-40405

cve-icon Vulnrichment

Updated: 2026-05-12T19:32:13.688Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-12T18:17:18.310

Modified: 2026-05-15T15:20:57.937

Link: CVE-2026-40405

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-13T10:00:10Z

Weaknesses