Affects Microsoft Exchange Online, a core service used across many enterprises; privilege escalation could lead to admin access and tenant compromise.
CVE-2026-54998
Exchange Online: privilege escalation via faulty authorization.
Is CVE-2026-54998 being exploited?
Not confirmed. CVE-2026-54998 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.78% probability of exploitation in the next 30 days.
How severe is CVE-2026-54998?
CVE-2026-54998 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-54998?
Yes. A fix has been recorded for CVE-2026-54998. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-54998 affect?
CVE-2026-54998 affects Microsoft Exchange Online. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-54998?
Patch when released; review and restrict privileged Exchange Online access.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authorized attacker can escalate to admin-level rights in Exchange Online.
Patch when possible