CVE-2026-54998 | Microsoft Exchange Online Elevation of Privilege Vulnerability

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

Published: 2026-07-02 Last update: 2026-07-07 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-54998 is rated Moderate Risk (51.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.64%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-54998

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-04 — 0.64% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-54998

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]

Weakness enumeration for CVE-2026-54998

GitHub Security Advisory for CVE-2026-54998

GHSA-phr2-vr74-whpx · Severity: high — Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate...

Affected software / configurations for CVE-2026-54998

Vendor Product Version Raw CPE
microsoft exchange_online — cpe:2.3:a:microsoft:exchange_online:-:*:*:*:*:*:*:*

References for CVE-2026-54998

cvelogic Threat Intelligence