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-2026-66808 Microsoft SharePoint Server Remote Code Execution Vulnerability New On this page  CVE-2026-66808  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Aug 11, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-66808  Impact Remote Code Execution Max Severity Important Weakness CWE-502: Deserialization of Untrusted Data CVSS Source Microsoft Vector String CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C Metrics CVSS:3.1 8.8 / 7.7  Base score metrics: 8.8 / Temporal score metrics: 7.7  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Network 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 Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code 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 Less Likely FAQ How could an attacker exploit the vulnerability? In a network-based attack, an authenticated attacker, as at least a Site Owner, could write arbitrary code to inject and execute code remotely on the SharePoint Server. 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. There are multiple update packages available for some of the affected software. Do I need to install all the updates listed in the Security Updates table for the software? Yes. Customers should apply all updates offered for the software installed on their systems. If multiple updates apply, they can be installed in any order. Acknowledgements 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 Aug 11, 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