CVE-2026-42897: Microsoft Exchange Server Cross-Site Scripting Vulnerability

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.

VendorMicrosoft
ProductMicrosoft
Date added to KEV2026-05-15
Due date (BOD 22-01)2026-05-29
Known ransomware campaign useUnknown
CWECWE-79
Required actionApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

What to do

  1. Identify every instance of Microsoft Microsoft in your environment (asset inventory, EDR, vulnerability scanner).
  2. Apply CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  3. Federal civilian agencies must act by 2026-05-29 under BOD 22-01; other organizations can use the same date as a target.
  4. Check the vendor advisory and NVD entry linked below for affected versions, then record the fix in your change log.

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Sources

Generated from the CISA feed with AI assistance; facts are taken verbatim from the feed. Not affiliated with or endorsed by CISA. Facts come from the CISA Known Exploited Vulnerabilities catalog (public domain).