Is It On KEV?

Microsoft Microsoft

YES - ON THE CISA KEV LIST
CVE-2026-42897

Microsoft Exchange Server Cross-Site Scripting Vulnerability

CISA catalog due date2026-05-29
166 days past due
EPSS exploit probability (next 30 days)70.7% · 99percentile
From CVE publication to KEV listing1 days (2026-05-14 → 2026-05-15)
Remediation window (KEV listing to due date)14 days
Days on the KEV list180 days
Date added to KEV2026-05-15
Known ransomware campaign useUnknown
VendorMicrosoft
ProductMicrosoft
Weaknesses (CWE)CWE-79

Microsoft: 391 entries (22.0% of all KEV entries are from this vendor); 41 added in 2026.

BOD 26-04 note: this is the date printed in the CISA catalog. A federal agency's actual deadline is set by its SSVC tier - Act (3 days), Attend (14 days), Track (60 days), or the next scheduled upgrade - counted from the KEV listing date or the date the vulnerability is identified in its environment, whichever comes first. Use the tier helper on each CVE page for your own window.

Your BOD 26-04 window (SSVC tier helper)

Your remediation window ends:

Description

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.

Required action (CISA)

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Notes

https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-42897 ; https://learn.microsoft.com/en-us/exchange/plan-and-deploy/post-installation-tasks/security-best-practices/exchange-emergency-mitigation-service ; https://nvd.nist.gov/vuln/detail/CVE-2026-42897

References

Other KEV entries for this vendor: Microsoft

Microsoft - Vendors with KEV entries

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