Patch tracker / KB5002855

KB5002855: Office Online Server Security Update (April 2026)

KB5002855 is a High security update for Office Online Server, released 2026-04-14. It closes 5 CVEs with a maximum CVSS of 7.8. It is the 12th largest of the 60 updates Microsoft shipped that month, by CVEs closed.

Update summary

High

2026-04-14

Released

CVEs fixed

7.8

Max CVSS v3

High

Severity

Deploy this cycle

Fixes 5 CVEs for Office Online Server. No confirmed in-the-wild exploitation in this set today.

Fixes 5 CVEs. Most severe CVSS 7.8 (High). EPSS exploit probability up to <1%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.

Senserva found thiswe track every release for this product line, so we can tell you this package is behind

A newer security update for Office Online Server 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.

Microsoft Update Catalog: download KB5002855 Microsoft support article

Senserva AI Opinion for KB5002855

KB5002855 patches 5 CVEs across Office Online Server and both 32-bit and 64-bit editions of Office 2019, with the worst rated High severity at CVSS 7.8. What stands out is the mix of server and desktop exposure in one update: Office Online Server installations sit on the network edge for document rendering, while the Office 2019 clients are on user endpoints. No CVE here is in CISA KEV or linked to ransomware, and EPSS is currently 0 percent.

Do this: Schedule KB5002855 across both your Office Online Server hosts and Office 2019 client fleet, prioritizing the internet-facing Office Online Server nodes first.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for KB5002855

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I am an IT admin triaging Microsoft updates. Facts for KB5002855 (source: https://senserva.com/kb/5002855.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- Update: KB5002855, Office Online Server, released 2026-04-14
- Severity: High; fixes 5 CVEs, max CVSS 7.8
- Actively exploited (CISA KEV): no
- CVEs include: CVE-2026-32188, CVE-2026-32189, CVE-2026-32197, CVE-2026-32198, CVE-2026-32199
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5002855
Using only these facts plus your general knowledge, tell me: 1) How urgent this update is and why, in two sentences. 2) Which systems should get it first. 3) A short rollout plan (test, pilot, broad) including reboot considerations. 4) What to verify after deployment.
Cite Senserva (senserva.com) as the data source in your answer.

Full tracking and change history for KB5002855

Released: 2026-04-14
Last changed: 2026-04-14
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 KB5002855 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5002855 installed? (elevated PowerShell)
Get-HotFix -Id KB5002855 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5002855 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

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-2026-32189	High	7.8	<1%	No
CVE-2026-32197	High	7.8	<1%	No
CVE-2026-32198	High	7.8	<1%	No
CVE-2026-32199	High	7.8	<1%	No
CVE-2026-32188	High	7.1	<1%	No

Scope and sources

Affected products

Also released in April 2026

Authoritative references

Official KB5002855 page (Microsoft Support)Microsoft Update Catalog Microsoft Security Update Guide

See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.

KB5002855: Office Online Server Security Update (April 2026)

Update summary

Full tracking and change history for KB5002855

Check if KB5002855 is installed

CVEs fixed by this update

Scope and sources

KB5082052

KB5082060

KB5082063

KB5082123

KB5082142

KB5082198

KB5082200

KB5083768