Microsoft Exchange Server Cross-Site Scripting Vulnerability

[ Why it matters ]Priority signals

• Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2026-05-15

[ Description ]Official description

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

CISA: 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.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 29 May 2026): Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ References ]References

• msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42897MitigationVendor Advisory
• www.cisa.gov/known-exploited-vulnerabilities-catalogUS Government Resource