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

criticalknown exploitedpublic exploitCVE-2026-42897
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
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.

CSIRTS triage

vendor: Microsoftproduct: Exchange ServerCross-site scripting
What
Microsoft Exchange Server contains a cross-site scripting vulnerability that can execute arbitrary JavaScript in the browser context.
Who is affected
Users of Microsoft Exchange Server are affected.
Urgency
Immediate remediation is necessary due to the critical severity and confirmed exploitation.
Action
Users should apply the latest patches provided by Microsoft.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
CISA Known Exploited Vulnerabilities (US · database · site)
Severity
critical
Published
2026-05-15
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-42897

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-42897coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Microsoft Exchange Server

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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