Microsoft Exchange Server Cross-Site Scripting Vulnerability (CVE-2026-42897)
Severity: medium · Patch status: unknown · Since 2026-05-15 · CVE-2026-42897
Microsoft Exchange Server contains a cross-site scripting vulnerability during web page generation in Outlook Web Access and when certain interaction conditions are met, arbitrary JavaScript can be executed in the browser context. CISA added CVE-2026-42897 to its Known Exploited Vulnerabilities catalog on May 15, 2026, which means attackers are exploiting it in the wild.
What to do
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- US federal agencies must remediate by May 29, 2026 (BOD 22-01); treat that as the outer limit.
Sources
All live incidents on Threat Watch