Patch tracker / KB5002877
KB5002877: Office Online Server Security Update (June 2026)
KB5002877 is a High security update for Office Online Server, released 2026-06-09. It closes 7 CVEs with a maximum CVSS of 8.2. It is the 11th largest of the 18 updates Microsoft shipped that month, by CVEs closed.
Update summary
Fixes 7 CVEs. Most severe CVSS 8.2 (High). EPSS exploit probability up to <1%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.
A newer security update for Microsoft Office 365 for Mac has shipped since this one: KB5002884 (2026-08-11). 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.
We checked Microsoft's support article for KB5002877 on 2026-08-12 and it lists no known issues. Read the article before broad deployment; Microsoft adds issues as reports come in, and we re-check on every refresh.
KB5002877 patches 7 vulnerabilities across a mixed Office footprint: Office 365 for Mac, Office Online Server, and Office 2019 32-bit editions. The top issue reaches High severity at CVSS 8.2, but exploitability signals are low, with a 1% EPSS and no CVE listed in CISA KEV or tied to ransomware. Because this bundle spans three distinct products, the same KB may map to different install paths and update channels in your environment.
Do this: Inventory which of the three affected products (Office 365 for Mac, Office Online Server, Office 2019 32-bit) you run and apply KB5002877 through each product's respective update channel.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5002877
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5002877
- Released
- 2026-06-09
- Last changed
- 2026-06-09
- Changes tracked
- 1
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 KB5002877 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-2026-44822 | High | 8.2 | <1% | No |
| CVE-2026-45455 | High | 8.2 | <1% | No |
| CVE-2026-44817 | High | 7.8 | <1% | No |
| CVE-2026-44820 | High | 7.8 | <1% | No |
| CVE-2026-44823 | High | 7.8 | <1% | No |
| CVE-2026-45469 | High | 7.8 | <1% | No |
| CVE-2026-44818 | High | 7.0 | <1% | No |
Scope and sources
- Affected products
- Also released in June 2026
KB5087423
66 CVEs · CriticalKB5087539
66 CVEs · CriticalKB5089466
61 CVEs · CriticalKB5089549
61 CVEs · CriticalKB5093998
158 CVEs · CriticalKB5094126
107 CVEs · CriticalKB5094128
105 CVEs · CriticalKB5002876
8 CVEs · HighThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.