What is CVE-2026-54998?
Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.
The record classifies CVE-2026-54998 under weakness class CWE-863. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 95 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.8 — HIGH
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 - EPSS (FIRST)
- 0.6% probability of exploitation in the next 30 days, higher than 46.4% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 6.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-07-02, last modified 2026-07-03
Is CVE-2026-54998 being exploited?
It currently carries a trending score of 41 in the Threadlinqs vulnerability feed.
Affected products and versions
- Microsoft: Exchange Online
How to fix CVE-2026-54998
No vendor patch reference has been recorded for CVE-2026-54998 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-54998
No threat campaign in the Threadlinqs corpus currently references CVE-2026-54998, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.
Sources
Enriched from CVE.org, NVD, GitHub Security Advisories, FIRST EPSS. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.