CVE-2026-55009: Microsoft Exchange Server

High severity, CVSS 7.8. EPSS: 2.5% chance of exploitation in the next 30 days.

Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.

Affected products

• Microsoft Exchange Server: version 2016 only; version 2019 only
• Microsoft Exchange Server Subscription Edition: before 15.02.2562.045 (fixed in 15.02.2562.045)

Published 2026-07-14. Last modified 2026-07-24.