Patch tracker / KB5066367
KB5066367: Microsoft Exchange Server Subscription Security Update (October 2025)
KB5066367 is a High security update for Microsoft Exchange Server Subscription, released 2025-10-14. It closes 3 CVEs with a maximum CVSS of 8.8. Get it from the Microsoft Update Catalog below, and see where it sits against the rest of the month on the patch tracker.
Update summary
New to these terms? How the Microsoft patching tools fit together, this month's Patch Tuesday summary, and every update ranked by real-world risk.
Senserva AI Opinion for KB5066367
KB5066367 patches three CVEs in Exchange Server, spanning the 2019 CU14 and CU15 builds plus the newer Subscription Edition RTM, with the worst rated High at CVSS 8.8 (CVE-2025-53782, CVE-2025-59249, CVE-2025-59248). Anyone still running on-premises Exchange is exposed, and Exchange remains a favorite target because it sits on the mail flow path and often holds elevated Active Directory rights. None are in CISA KEV yet and EPSS is only 1 percent, so you have a window to patch before exploitation matures rather than under active fire.
Do this: Confirm your Exchange servers are on a supported CU (2019 CU14, CU15, or Subscription Edition RTM) and schedule the KB5066367 update, since older CUs cannot receive this fix.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5066367
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5066367
Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.
Exploitation and severity
Fixes 3 CVEs. Most severe CVSS 8.8 (High). EPSS exploit probability up to <1%.
Among the lower half of tracked Microsoft updates by EPSS exploit probability.
What to do
Moderate priority: schedule it in your normal patch cycle. Senserva flags whether KB5066367 is missing on your devices.
Check if KB5066367 is installed
Copy-paste PowerShell: one machine, or your whole estate in one pass. No output means the update is not installed.
Get-HotFix covers Windows updates. Office, SharePoint, and Exchange server updates show under installed updates in Programs and Features, or check the Update Catalog history.
CVEs fixed by this update
Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.
| CVE | Severity | CVSS | EPSS | Exploited |
|---|---|---|---|---|
| CVE-2025-53782 | High | 8.8 | <1% | No |
| CVE-2025-59248 | High | 8.8 | <1% | No |
| CVE-2025-59249 | High | 8.8 | <1% | No |
Affected products
Also released in October 2025
The highest-risk updates from the same release:
The full month, summarized: Microsoft Patch Tuesday.
Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.