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Privacy Statement Third-Party Cookies AcceptRejectManage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-42903 Windows Kerberos Denial of Service Vulnerability New On this page  CVE-2026-42903  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Jun 9, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-42903  Impact Denial of Service Max Severity Important Weakness CWE-476: NULL Pointer Dereference CVSS Source Microsoft Vector String CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C Metrics CVSS:3.1 6.5 / 5.7  Base score metrics: 6.5 / Temporal score metrics: 5.7  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Network Attack Complexity Low Privileges Required Low User Interaction None Scope Unchanged Confidentiality None Integrity None Availability High   Temporal score metrics(3) Exploit Code Maturity Unproven Remediation Level Official Fix Report Confidence Confirmed Please see Common Vulnerability Scoring System for more information on the definition of these metrics. Executive Summary Null pointer dereference in Windows Kerberos allows an authorized attacker to deny service over a network. Exploitability The following table provides an exploitability assessment for this vulnerability at the time of original publication. Publicly disclosed No Exploited No Exploitability assessment Exploitation Unlikely Acknowledgements Andrew Schwartz 𝕏 @ 4ndr3w6s with Huntress Labs Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgements for more information. Security Updates To determine the support lifecycle for your software, see the Microsoft Support Lifecycle. Release date Descending  Edit columns  Download  Filters  Product Family  Max Severity  Impact  Platform   Clear Release date  Product Platform Impact Max Severity Article Download Build Number Assigning CNA Title: Release date, Content: Jun 9, 2026 Windows Server 2012 R2 (Server Core installation) - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2012 R2 (Server Core installation), Content:, 1 link 5094041  Title: Download Security Update for Windows Server 2012 R2 (Server Core installation), Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.3.9600.23228 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2012 R2 - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2012 R2, Content:, 1 link 5094041  Title: Download Security Update for Windows Server 2012 R2, Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.3.9600.23228 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2012 (Server Core installation) - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2012 (Server Core installation), Content:, 1 link 5094042  Title: Download Security Update for Windows Server 2012 (Server Core installation), Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.2.9200.26132 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2012 - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2012, Content:, 1 link 5094042  Title: Download Security Update for Windows Server 2012, Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.2.9200.26132 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2016 (Server Core installation) - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2016 (Server Core installation), Content:, 1 link 5094122  Title: Download Security Update for Windows Server 2016 (Server Core installation), Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.14393.9234 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2016 - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2016, Content:, 1 link 5094122  Title: Download Security Update for Windows Server 2016, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.14393.9234 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 10 Version 1607 for x64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 10 Version 1607 for x64-based Systems, Content:, 1 link 5094122  Title: Download Security Update for Windows 10 Version 1607 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.14393.9234 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 10 Version 1607 for 32-bit Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 10 Version 1607 for 32-bit Systems, Content:, 1 link 5094122  Title: Download Security Update for Windows 10 Version 1607 for 32-bit Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.14393.9234 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 26H1 for ARM64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 26H1 for ARM64-based Systems, Content:, 1 link 5095051  Title: Download Security Update for Windows 11 Version 26H1 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.28000.2269 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 version 26H1 for x64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 version 26H1 for x64-based Systems, Content:, 1 link 5095051  Title: Download Security Update for Windows 11 version 26H1 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.28000.2269 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2025 - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2025, Content:, 1 link 5094125  Title: Download Security Update for Windows Server 2025, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26100.32995 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 24H2 for x64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 24H2 for x64-based Systems, Content:, 1 link 5094126  Title: Download Security Update for Windows 11 Version 24H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26100.8655 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 24H2 for ARM64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 24H2 for ARM64-based Systems, Content:, 1 link 5094126  Title: Download Security Update for Windows 11 Version 24H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26100.8655 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 23H2 for x64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 23H2 for x64-based Systems, Content:, 1 link 5093998  Title: Download Security Update for Windows 11 Version 23H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.22631.7219 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 23H2 for ARM64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 23H2 for ARM64-based Systems, Content:, 1 link 5093998  Title: Download Security Update for Windows 11 Version 23H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.22631.7219 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 25H2 for x64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 25H2 for x64-based Systems, Content:, 1 link 5094126  Title: Download Security Update for Windows 11 Version 25H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26200.8655 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 11 Version 25H2 for ARM64-based Systems - Denial of Service Important Title: Knowledge Base Articles for Windows 11 Version 25H2 for ARM64-based Systems, Content:, 1 link 5094126  Title: Download Security Update for Windows 11 Version 25H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26200.8655 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows Server 2025 (Server Core installation) - Denial of Service Important Title: Knowledge Base Articles for Windows Server 2025 (Server Core installation), Content:, 1 link 5094125  Title: Download Security Update for Windows Server 2025 (Server Core installation), Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26100.32995 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jun 9, 2026 Windows 10 Version 22H2 for 32-bit Systems - Denial of Service