HIGH: Microsoft Exchange Server XSS Flaw CVE-2026-42897 Under Active Attack
Microsoft Exchange Server CVE-2026-42897 is a cross-site scripting flaw in Outlook Web Access that lets a crafted email execute JavaScript in the victim OWA session. CISA added it to the Known Exploited Vulnerabilities catalog on May 15, 2026 after confirmed in-the-wild exploitation, with a May 29 federal mitigation deadline. Exchange Server 2016, 2019, and Subscription Edition are affected. Exchange Online is not. Microsoft scored it CVSS 8.1, and patches shipped in the May 2026 security update.