Patch tracker / KB5063221
KB5063221: Exchange Server 2019 Cumulative Update Security Update (August 2025)
KB5063221 is a High security update for Exchange Server 2019 Cumulative Update, released 2025-08-12. It closes 4 CVEs with a maximum CVSS of 7.5. It is the 20th largest of the 44 updates Microsoft shipped that month, by CVEs closed.
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Update summary
Fixes 4 CVEs. Most severe CVSS 7.5 (High). EPSS exploit probability up to 1.4%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.
A newer security update for Microsoft Exchange Server 2019 Cumulative Update 15 has shipped since this one: KB5128896 (2026-10-13). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.
KB5063221 is the August 2025 Exchange on-premises security update covering Exchange 2016 CU23 and Exchange 2019 CU14 and CU15, addressing four CVEs (CVE-2025-33051, CVE-2025-25005, CVE-2025-25006, CVE-2025-25007). The highest severity is High at CVSS 7.5, and none of the four are in CISA KEV or linked to ransomware, with EPSS peaking at only 1 percent. It matters because it applies only to organizations still running Exchange on-premises, where mailbox servers are internet-facing and historically targeted after patch details become public.
Do this: Confirm your Exchange servers are on 2016 CU23, 2019 CU14, or 2019 CU15, then schedule and apply KB5063221 during your next maintenance window.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5063221
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5063221
- Released
- 2025-08-12
- Last changed
- 2026-09-26
- Changes tracked
- 2
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.
Check if KB5063221 is installed
Elevated PowerShell. No output means it is not installed.
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-2025-33051 | High | 7.5 | 1.3% | No |
| CVE-2025-25005 | Medium | 6.5 | 1.4% | No |
| CVE-2025-25006 | Medium | 5.3 | <1% | No |
| CVE-2025-25007 | Medium | 5.3 | <1% | No |
Scope and sources
- Affected products
- Also released in August 2025
KB5063709
44 CVEs · CriticalKB5063812
56 CVEs · CriticalKB5063871
48 CVEs · CriticalKB5063875
47 CVEs · CriticalKB5063877
54 CVEs · CriticalKB5063878
61 CVEs · CriticalKB5063880
56 CVEs · CriticalKB5063888
34 CVEs · CriticalThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.