Auth bypass in Microsoft Exchange Server 2016 Cumulative Update 23
CVE-2025-53786
On April 18th 2025, Microsoft announced Exchange Server Security Changes for Hybrid Deployments and accompanying non-security Hot Fix. Microsoft made these changes in the general interest of improving the security of hybrid Exchange deploy…
Vulnerability class: Broken Authentication
EPSS: 0.005 (68.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C.
Affected products
- 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)
Public proof-of-concept exploits
References
- Microsoft Exchange Server Hybrid Deployment Elevation of Privilege Vulnerability (vendor-advisory, patch)
Frequently asked questions
- What is CVE-2025-53786?
- CVE-2025-53786 is a high-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, classified under Improper Authentication. CVSS score: 8.0/10. Published 2025-08-06.
- How severe is CVE-2025-53786?
- High severity. CVSS v3 base score is 8.0 out of 10.
- Is CVE-2025-53786 known to be exploited?
- 11 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.