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CVE-2026-55008: Microsoft Exchange Server Spoofing Vulnerability

criticalCVSS 9.6CVE-2026-55008
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.

CSIRTS triage

vendor: Microsoftproduct: Microsoft Exchange ServerCross-site scripting
What
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.
Who is affected
Unauthorized users targeting Microsoft Exchange Server deployments.
Urgency
Remediation is critical due to the high severity and potential for widespread spoofing attacks.
Action
Apply the latest security patch for Microsoft Exchange Server.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
critical — CVSS 9.6
Published
2026-07-14
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55008

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-2026-55008coverage & 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.

More from Microsoft Security Response Center