CVE entry · CVE-2026-42897
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.
- Actively exploited: added to CISA’s KEV catalog on May 15, 2026.
- Use by ransomware: not established so far.
- Remediation deadline for US federal agencies: May 29, 2026.
- CERT-FR alert CERTFR-2026-ALE-005 of May 15, 2026.
Description from CISA’s KEV catalog.
CERT-FR alerts and notices
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CERTFR-2026-ALE-005[Màj] Vulnérabilité dans Microsoft Exchange Server (15 mai 2026)
What to do
- Check whether your estate includes Microsoft, including internet-facing devices.
- Apply the vendor’s patch or mitigations (references below). Failing that, isolate the product or stop using it, as CISA requires of US federal agencies.
- An exploited vulnerability has often been used before it was fixed: look for signs of compromise, especially on internet-facing devices.
References
- Vendor advisory or reference cited by CISA (msrc.microsoft.com)
- Vendor advisory or reference cited by CISA (learn.microsoft.com)
- NVD entry (NIST)
- CISA KEV catalog
Other Microsoft vulnerabilities
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Microsoft Windows Command Injection Vulnerability
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Microsoft SharePoint Code Injection Vulnerability
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Microsoft Windows Heap-Based Buffer Overflow Vulnerability
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Microsoft Windows Link Following Vulnerability
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Microsoft SQL Server Remote Code Execution Vulnerability
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Microsoft SharePoint Weak Authentication Vulnerability