- What: Microsoft discloses a privilege escalation vulnerability in Windows TCP/IP stack
- Impact: Local attackers could gain elevated privileges on affected systems
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 Accept Reject Manage cookies MSRC Customer Guidance Security Update Guide Vulnerabilities CVE-2026-34351 Windows TCP/IP Elevation of Privilege Vulnerability New On this page CVE-2026-34351 Subscribe RSS PowerShell API CSAF Security Vulnerability Released: May 12, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-34351 Impact Elevation of Privilege Max Severity Important Weakness CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') CVSS Source Microsoft Vector String CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C Metrics CVSS:3.1 7.8 / 6.8 Base score metrics: 7.8 / Temporal score metrics: 6.8 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 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 Concurrent execution using shared resource with improper synchronization ('race condition') in Windows TCP/IP allows an authorized 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. Acknowledgements hazard 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 Loading... 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