Auth bypass in Microsoft Exchange Server
CVE-2026-45503
Improper authorization in Microsoft Exchange Server allows an authorized attacker to disclose information over a network.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.009 (57.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 57.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.009 · change: +0.004
Affected products
- Microsoft Exchange Server — versions 2016, 2019
- Microsoft Exchange Server Subscription Edition
- Microsoft Exchange Server 2016 Cumulative Update 23 — versions 15.01.0.0
- Microsoft Exchange Server 2019 Cumulative Update 14 — versions 15.02.0.0
- Microsoft Exchange Server 2019 Cumulative Update 15 — versions 15.02.0.0
- Microsoft Exchange Server Subscription Edition Rtm — versions 15.02.0.0
Weakness classification (CWE)
References
- Microsoft Exchange Server Information Disclosure Vulnerability (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-45503?
- CVE-2026-45503 is a high-severity vulnerability in Microsoft Exchange Server, classified under Improper Authorization. CVSS score: 8.1/10. Published 2026-06-09.
- How severe is CVE-2026-45503?
- High severity. CVSS v3 base score is 8.1 out of 10.