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-2026-42915 Windows TCP/IP Denial of Service Vulnerability New On this page  CVE-2026-42915  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Jun 9, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-42915  Impact Denial of Service Max Severity Important Weakness CWE-131: Incorrect Calculation of Buffer Size CVSS Source Microsoft Vector String CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C Metrics CVSS:3.1 5.7 / 5.0  Base score metrics: 5.7 / Temporal score metrics: 5.0  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Adjacent 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 Incorrect calculation of buffer size in Windows TCP/IP allows an authorized attacker to deny service over an adjacent 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 Less Likely FAQ According to the CVSS metric, the attack vector is adjacent (AV:A). What does that mean for this vulnerability? An authenticated attacker could exploit this vulnerability with LAN access. Acknowledgements Jungwoo Lee 𝕏 @ physicube with KAIST SoftSec Lab https://softsec.kaist.ac.kr/ Wongi Lee 𝕏 @ _qwerty_po with Theori https://xint.io/ Calif.io and Milad Nasr (Anthropic) with Claude with Calif.io and Anthropic Anonymous 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 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 Jun 9, 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