How severe is CVE-2026-54998?

CVE-2026-54998 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-54998 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-54998?

CVE-2026-54998 affects Microsoft Exchange Online. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-54998?

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

When was CVE-2026-54998 published?

CVE-2026-54998 was published on 2026-07-02 and last updated on 2026-07-07.

CVE-2026-54998

CVE-2026-54998 is a high-severity vulnerability in Microsoft Exchange Online with a CVSS 3.x base score of 8.8. 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-863.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Microsoft Exchange Online
Published: 2026-07-02
Last modified: 2026-07-07

Description

Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.

Frequently asked questions

What is CVE-2026-54998?: Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.
How severe is CVE-2026-54998?: CVE-2026-54998 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-54998 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-54998?: CVE-2026-54998 affects Microsoft Exchange Online. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-54998?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-54998 published?: CVE-2026-54998 was published on 2026-07-02 and last updated on 2026-07-07.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54998

Affected products (1)

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

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