---
id: CVE-2026-54998
title: Microsoft Exchange Online Elevation of Privilege Vulnerability
summary: >-
  Incorrect authorization in Microsoft Exchange Online allows an authorized
  attacker to elevate privileges over a network.
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'
cvssSource: cna
cwe:
  - CWE-863
vendor: Microsoft
product: Microsoft Exchange Online
affected:
  - exchange_online -
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-07-06T00:00:00+00:00'
exploitAvailable: true
published: '2026-07-02'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T18:19:40.079Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-54998'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54998'
    label: Microsoft Exchange Online Elevation of Privilege Vulnerability
tags:
  - cve.org
  - exploit-available
epss: 0.00778
epssPercentile: 0.53994
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/sentinel-aidefense/CVE-2026-54998-exp'
  checkedAt: '2026-09-26T09:05:49.806Z'
ingestedAt: '2026-09-08T17:06:31.933Z'
---

## Overview

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

## Affected

- `exchange_online -`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.