CVE-2026-48579: Improper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information ov

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CRITICAL 9.1REMOTEWATCHLISTMITIGATE

CVE-2026-48579 is a critical-severity flaw (CVSS 9.1) affecting exchange online. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a network.

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-285
Published	2026-06-04
Last modified	2026-07-23

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-07-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-04 23:17 UTCPublished CVE record published
2026-07-23 07:10 UTCUpdated Record last modified

microsoft exchange online MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy exchange-online || rpm -q exchange-online || exchange-online --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · arm-none-eabi-binutils-cs · FIXED · 2.47-1.fc46 · FEDORA-2026-7498616952 · source

sudo dnf upgrade --advisory=FEDORA-2026-7498616952

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-48579?

exchange online: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-48579 being exploited?

CVE-2026-48579 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-48579 affect?

CVE-2026-48579 affects exchange online. Severity is critical (CVSS 9.1). Improper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a network.

How urgent is CVE-2026-48579?

Priority 61/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Microsoft Exchange vulnerabilities

Related CVEs

CVE-2026-48582 CRITICAL 9.6 MITIGATE Missing authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a
CVE-2026-54998 HIGH 8.8 MITIGATE Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over
CVE-2026-56191 CRITICAL 10.0 MITIGATE Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over
CVE-2026-65801 CRITICAL 10.0 MITIGATE Server-side request forgery (ssrf) in Microsoft Exchange Online allows an unauthorized attacker to elevate pri

References

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