We use optional cookies to improve your experience on our websites, such as through social media connections, and to display personalized advertising based on your online activity. If you reject optional cookies, only cookies necessary to provide you the services will be used. You may change your selection by clicking “Manage Cookies” at the bottom of the page. Privacy Statement Third-Party Cookies AcceptRejectManage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-49801 Windows SMB Information Disclosure Vulnerability New On this page  CVE-2026-49801  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Jul 14, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-49801  Impact Information Disclosure Max Severity Important Weakness CWE-908: Use of Uninitialized Resource CVSS Source Microsoft Vector String CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C Metrics CVSS:3.1 5.5 / 4.8  Base score metrics: 5.5 / Temporal score metrics: 4.8  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Local Attack Complexity Low Privileges Required Low User Interaction None Scope Unchanged Confidentiality High Integrity None Availability None   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 Use of uninitialized resource in Windows SMB allows an authorized attacker to disclose information locally. 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 Less Likely Acknowledgements sweetchip 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: Jul 14, 2026 Windows Server 2022 - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2022, Content:, 1 link 5099540  Title: Download Security Update for Windows Server 2022, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.20348.5386 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2019 (Server Core installation) - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2019 (Server Core installation), Content:, 1 link 5099538  Title: Download Security Update for Windows Server 2019 (Server Core installation), Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.17763.9020 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2019 - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2019, Content:, 1 link 5099538  Title: Download Security Update for Windows Server 2019, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.17763.9020 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 1809 for x64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 1809 for x64-based Systems, Content:, 1 link 5099538  Title: Download Security Update for Windows 10 Version 1809 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.17763.9020 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2012 R2 - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2012 R2, Content:, 1 link 5099444  Title: Download Security Update for Windows Server 2012 R2, Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.3.9600.23291 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2012 (Server Core installation) - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2012 (Server Core installation), Content:, 1 link 5099445  Title: Download Security Update for Windows Server 2012 (Server Core installation), Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.2.9200.26226 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 11 Version 25H2 for x64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 11 Version 25H2 for x64-based Systems, Content:, 1 link 5101650  Title: Download Security Update for Windows 11 Version 25H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26200.8875 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 11 Version 25H2 for ARM64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 11 Version 25H2 for ARM64-based Systems, Content:, 1 link 5101650  Title: Download Security Update for Windows 11 Version 25H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26200.8875 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2025 (Server Core installation) - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2025 (Server Core installation), Content:, 1 link 5099536  Title: Download Security Update for Windows Server 2025 (Server Core installation), Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.26100.33158 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 22H2 for 32-bit Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 22H2 for 32-bit Systems, Content:, 1 link 5099539  Title: Download Security Update for Windows 10 Version 22H2 for 32-bit Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.19045.7548 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 22H2 for ARM64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 22H2 for ARM64-based Systems, Content:, 1 link 5099539  Title: Download Security Update for Windows 10 Version 22H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.19045.7548 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 22H2 for x64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 22H2 for x64-based Systems, Content:, 1 link 5099539  Title: Download Security Update for Windows 10 Version 22H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.19045.7548 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 21H2 for x64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 21H2 for x64-based Systems, Content:, 1 link 5099539  Title: Download Security Update for Windows 10 Version 21H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.19044.7548 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 21H2 for ARM64-based Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 21H2 for ARM64-based Systems, Content:, 1 link 5099539  Title: Download Security Update for Windows 10 Version 21H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.19044.7548 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 21H2 for 32-bit Systems - Information Disclosure Important Title: Knowledge Base Articles for Windows 10 Version 21H2 for 32-bit Systems, Content:, 1 link 5099539  Title: Download Security Update for Windows 10 Version 21H2 for 32-bit Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.19044.7548 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2012 - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2012, Content:, 1 link 5099445  Title: Download Security Update for Windows Server 2012, Content:, 1 link Monthly Rollup  Title: Build numbers, Content: 6.2.9200.26226 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2016 (Server Core installation) - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2016 (Server Core installation), Content:, 1 link 5099535  Title: Download Security Update for Windows Server 2016 (Server Core installation), Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.14393.9339 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows Server 2016 - Information Disclosure Important Title: Knowledge Base Articles for Windows Server 2016, Content:, 1 link 5099535  Title: Download Security Update for Windows Server 2016, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.14393.9339 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Jul 14, 2026 Windows 10 Version 1607 for x64-based Systems - Information Disclosure Important