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CVE-2026-42904

Windows TCP/IP Elevation of Privilege Vulnerability

Published: Jun 9, 2026Updated: Jun 11, 2026 Sources: CVE List NVD BDUCWE-122
9.6CRITICAL
NVD MITRE
EPSS Score
0.4%
Top 65.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

Heap-based buffer overflow in Windows TCP/IP allows an unauthorized attacker to elevate privileges over an adjacent network.

In plain language

AI Act now

CVE-2026-42904 is a Windows TCP/IP security flaw that can let an attacker with network access gain higher privileges; small businesses should patch quickly because the affected versions include common Windows 10/11 and Windows Server systems.

Executive summary

CVE-2026-42904 is a Windows TCP/IP heap-based buffer overflow that can be triggered via network traffic (no user interaction required) to achieve elevation of privilege; Microsoft has fixes available for multiple Windows 10/11 and Windows Server builds.

If affected, business impact
Admin-level takeover from networkMalware and ransomware enablementWidest impact across Windows hostsService disruption from compromise

What to do now

  1. Check whether your systems run one of the affected Windows versions (Windows 10/11 and Windows Server 2012–2025, including the 26H1 extra case).
  2. For each affected system, confirm it is already at (or above) one of the listed fixed build numbers.
  3. Install the Microsoft security update for CVE-2026-42904 and reboot if your update process requires it.
  4. Verify update success (installed update present) and re-check the build number after reboot.
Patch / advisory Usually a quick update

CVSS Vector Breakdown

AV:AAC:LPR:NUI:NS:CC:HI:HA:H
Exploitability
AV:AAttack Vector
Adjacent
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-122

Affected Products

Microsoft Corp
commercial·USaka Microsoft, microsoft corporation
Windows 10 Version 21H2On-premOS
Operating Systems / windows
Windows 11 version 23H2On-premOS
Operating Systems / windows
Windows Server 2022 (Server Core installation)On-premOS
Operating Systems / windows
Windows Server 2025 (Server Core installation)On-premOS
Operating Systems / windows
Windows Server 2019 (Server Core installation)On-premOS
Operating Systems / windows
Windows Server 2016 (Server Core installation)On-premOS
Operating Systems / windows
Windows Server 2012 R2 (Server Core installation)On-premOS
Operating Systems / windows
Windows Server 2012 (Server Core installation)On-premOS
Operating Systems / windows
and 31 more affected products View all →

Exploitability

Official Patch Available
Is your org exposed to CVE-2026-42904?We can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

Click technique nodes for MITRE ATT&CK details · drag to pan · Ctrl/⌘ + scroll to zoom, or go fullscreen.

MITRE ATT&CK

1 technique
Privilege Escalation
View detailed technique mapping

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42904
msrc.microsoft.com
News mentions
4

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