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-2026-42897 Microsoft Exchange Server Spoofing Vulnerability New On this page  CVE-2026-42897  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: May 14, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-42897  Impact Spoofing Max Severity Critical Weakness CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CVSS Source Microsoft Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C Metrics CVSS:3.1 8.1 / 7.5  Base score metrics: 8.1 / Temporal score metrics: 7.5  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Network Attack Complexity Low Privileges Required None User Interaction Required Scope Unchanged Confidentiality High Integrity High Availability None   Temporal score metrics(3) Exploit Code Maturity Functional Remediation Level Official Fix Report Confidence Confirmed Please see Common Vulnerability Scoring System for more information on the definition of these metrics. Executive Summary Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network. Exploitability The following table provides an exploitability assessment for this vulnerability at the time of original publication. Publicly disclosed No Exploited Yes Exploitability assessment Exploitation Detected FAQ How could an attacker exploit this vulnerability? An attacker could exploit this issue by sending a specially crafted email to a user. If the user opens the email in Outlook Web Access and certain interaction conditions are met, arbitrary JavaScript can be executed in the browser context. How do I protect my Exchange Server from this vulnerability? The Exchange Emergency Mitigation Service will provide mitigation automatically, and is on by default. If it is not already enabled on your Exchange Server, you need to enable Exchange Emergency Mitigation Service. You can find more information and instruction in the Exchange blog here. Why are there no links to updates in the Security Update Table? Microsoft is supplying a temporary mitigation for this vulnerability through the Exchange Emergency Mitigation Service. We are working on developing and testing a more permanent fix which we will provide when it meets our quality standards. 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 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 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