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Privacy Statement Third-Party Cookies Accept Reject Manage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-40402 Windows Hyper-V Elevation of Privilege Vulnerability New On this page  CVE-2026-40402  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: May 12, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-40402  Impact Elevation of Privilege Max Severity Critical Weakness CWE-416: Use After Free CVSS Source Microsoft Vector String CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C Metrics CVSS:3.1 9.3 / 8.1  Base score metrics: 9.3 / Temporal score metrics: 8.1  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Local Attack Complexity Low Privileges Required None User Interaction None Scope Changed Confidentiality High Integrity High 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 Use after free in Windows Hyper-V allows an unauthorized attacker to elevate privileges 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 FAQ What privileges could be gained by an attacker who successfully exploited this vulnerability? An attacker who successfully exploited this vulnerability could gain SYSTEM privileges. Under what circumstances might this vulnerability be exploited other than as a denial of service attack against a Hyper-V host? This issue allows a guest VM to force the Hyper-V host's kernel to read from an arbitrary, potentially invalid address. The contents of the address read would not be returned to the guest VM. In most circumstances, this would result in a denial of service of the Hyper-V host (bugcheck) due to reading an unmapped address. It is possible to read from a memory mapped device register corresponding to a hardware device attached to the Hyper-V host which may trigger additional, hardware device specific side effects that could compromise the Hyper-V host's security. According to the CVSS metric, a successful exploitation could lead to a scope change (S:C). What does this mean for this vulnerability? In this case, a successful attack could be performed from a low privilege Hyper-V guest. The attacker could traverse the guest's security boundary to gain access to the Hyper-V host environment. Acknowledgements Ashutosh 𝕏 @ 0xashutosh with skyhighsecurity https://www.skyhighsecurity.com/ 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 Customer Action Required Title: Release date, Content: May 12, 2026 Windows 11 Version 23H2 for x64-based Systems - Elevation of Privilege Critical Title: Knowledge Base Articles for Windows 11 Version 23H2 for x64-based Systems, Content:, 1 link 5087420  Title: Download Security Update for Windows 11 Version 23H2 for x64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.22631.7079 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Windows 11 Version 23H2 for ARM64-based Systems - Elevation of Privilege Critical Title: Knowledge Base Articles for Windows 11 Version 23H2 for ARM64-based Systems, Content:, 1 link 5087420  Title: Download Security Update for Windows 11 Version 23H2 for ARM64-based Systems, Content:, 1 link Security Update  Title: Build numbers, Content: 10.0.22631.7079 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Windows Server 2022 (Server Core installation) - Elevation of Privilege Critical Title: Knowledge Base Articles for Windows Server 2022 (Server Core installation), Content:, 2 links 5087545  5087424  Title: Download Security Update for Windows Server 2022 (Server Core installation), Content:, 2 links Security Update  Security Hotpatch Update  Title: Build numbers, Content: 10.0.20348.5139 10.0.20348.5074 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Windows Server 2022 - Elevation of Privilege Critical Title: Knowledge Base Articles for Windows Server 2022, Content:, 2 links 5087545  5087424  Title: Download Security Update for Windows Server 2022, Content:, 2 links Security Update  Security Hotpatch Update  Title: Build numbers, Content: 10.0.20348.5139 10.0.20348.5074 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required All results loaded Loaded all 4 rows Disclaimer The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. Revisions version revisionDate description 1.0 May 12, 2026 Information published.  How satisfied are you with the MSRC Security Update Guide? Rating  Broken  Bad  Below average  Average  Great!  Your Privacy Choices Consumer Health Privacy