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CVE-2026-48579: Microsoft Exchange Online Information Disclosure Vulnerability

criticalCVSS 9.1CVE-2026-48579
Improper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a network.

CSIRTS triage

vendor: Microsoftproduct: Exchange OnlineInformation disclosure
What
Improper authorization allows unauthorized information disclosure over a network.
Who is affected
Users of Microsoft Exchange Online.
Urgency
Critical urgency due to the potential for information disclosure with a CVSS score of 9.1.
Action
Implement recommended security measures and monitor for unauthorized access.

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

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
critical — CVSS 9.1
Published
2026-06-09
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-48579

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-2026-48579coverage & exploitation statusNVD · CVE.org

Recent advisories for Microsoft Exchange Online

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