How severe is CVE-2026-48579?

CVE-2026-48579 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-48579 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-48579?

CVE-2026-48579 affects Microsoft Exchange Online. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-48579?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-48579 have an EU (EUVD) identifier?

Yes. CVE-2026-48579 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34338.

When was CVE-2026-48579 published?

CVE-2026-48579 was published on 2026-06-04 and last updated on 2026-06-17.

CVE-2026-48579

CVE-2026-48579 is a critical-severity vulnerability in Microsoft Exchange Online with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-285.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 1% (59th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-34338
Weakness: CWE-285
Affected product: Microsoft Exchange Online
Published: 2026-06-04
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2026-48579?: Improper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a network.
How severe is CVE-2026-48579?: CVE-2026-48579 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-48579 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-48579?: CVE-2026-48579 affects Microsoft Exchange Online. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-48579?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-48579 have an EU (EUVD) identifier?: Yes. CVE-2026-48579 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34338.
When was CVE-2026-48579 published?: CVE-2026-48579 was published on 2026-06-04 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:microsoft:exchange_online:-:*:*:*:*:*:*:*

More vulnerabilities in Microsoft Exchange Online

CVE-2026-48582 — Critical (CVSS 9.6): Missing authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.
CVE-2026-54998 — High (CVSS 8.8): Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.

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