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-2026-55040 Microsoft SharePoint Server Security Feature Bypass Vulnerability New On this page  CVE-2026-55040  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Jul 14, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-55040  Impact Security Feature Bypass Max Severity Critical Weakness CWE-1390: Weak Authentication CVSS Source Microsoft Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C Metrics CVSS:3.1 9.1 / 7.9  Base score metrics: 9.1 / Temporal score metrics: 7.9  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Network Attack Complexity Low Privileges Required None User Interaction None Scope Unchanged Confidentiality High Integrity High 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 Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature 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 More Likely FAQ What kind of security feature could be bypassed by successfully exploiting this vulnerability? The authentication feature could be bypassed as this vulnerability allows impersonation. I am running SharePoint Server 2016. Do the updates for SharePoint Enterprise Server 2016 also apply to the version I am running? Yes. The same KB number applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Customers running either version should install the security update to be protected from this vulnerability. According to the CVSS metrics, successful exploitation of this vulnerability could lead to major loss of confidentiality (C:H), and integrity (I:H), but could lead to no loss of availability (A:N). What does that mean for this vulnerability? Exploiting this vulnerability could allow an attacker to disclose files and modify data, but the attacker cannot impact the availability of the system. How could an attacker exploit this vulnerability? In a network-based attack, an unauthenticated attacker could bypass authentication and make an anonymous connection. Acknowledgements 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 Jul 14, 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 Privacy & Cookies