CVE-2025-64666: Microsoft Exchange Server

High severity, CVSS 7.5. EPSS: 1% chance of exploitation in the next 30 days.

Improper input validation in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

Affected products

• Microsoft Exchange Server: version 2016 only; version 2019 only
• Microsoft Exchange Server Subscription Edition: before 15.02.2562.035 (fixed in 15.02.2562.035)

Published 2025-12-09. Last modified 2026-06-17.