Microsoft has released security updates addressing a spoofing vulnerability (CVE-2026-42897, CVSS 8.1 HIGH) in Exchange Server that is already being exploited in the wild, allowing for remote arbitrary code execution without authentication. The NVD data indicates affected versions include Microsoft Exchange Server 2016, though specific version ranges are not provided. The solution is to apply the June 2026 security updates via Microsoft Update or the Microsoft Update Catalog.
JPCERT-AT-2026-0017 JPCERT/CC 2026-06-10 I. Overview Microsoft has released June 2026 Security Updates to address the vulnerabilities in their products. Attackers leveraging these vulnerabilities may be able to execute arbitrary code remotely without authentication, etc. Microsoft Corporation June 2026 Security Updates https://msrc.microsoft.com/update-guide/en-US/releaseNote/2026-Jun Microsoft has announced that the following vulnerability, disclosed on May 14, has been exploited in the wild. Please refer to the latest information provided by Microsoft and implement the measures described in "II. Solution." CVE-2026-42897 Microsoft Exchange Server Spoofing Vulnerability https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-42897 II. Solution Please apply the security update programs through Microsoft Update, Windows Update, etc. Microsoft Update Catalog https://www.catalog.update.microsoft.com/ Windows Update: FAQ https://support.microsoft.com/en-us/help/12373/windows-update-faq III. References Microsoft Corporation Release Notes https://msrc.microsoft.com/update-guide/ If you have any information regarding this alert, please contact JPCERT/CC. JPCERT Coordination Center (Cyber Security Coordination Group) MAIL: ew-info@jpcert.or.jp https://www.jpcert.or.jp/english/ Top