Patch tracker / KB5002910

KB5002910: Office Online Server Security Update (September 2026)

KB5002910 is a High security update for Office Online Server, released 2026-09-08. It closes 5 CVEs with a maximum CVSS of 7.8. Microsoft documents 1 known issue for this update, quoted below.

Before you deploy: Microsoft lists 1 known issue for this update.

In Excel Online, the paste operation might fail silently. Although users try to paste content, the source remains selected and the destination is...

Known issues

Our data comes from Microsoft, CISA and other public sources, and it can be wrong or out of date. If you are unsure, check the linked source before you act, and tell us when we are wrong so we can fix it.

Update summary

High

2026-09-08

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: KB5002928 (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.

Senserva found thisread these before you deploy broadly

Microsoft documents 1 known issue with this update.

In Excel Online, the paste operation might fail silently. Although users try to paste content, the source remains selected and the destination is...

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5002910 Microsoft support article

Senserva AI Opinion and rich prompt for KB5002910

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 KB5002910 (source: https://senserva.com/kb/5002910.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed daily (early morning US Central)):
- Update: KB5002910, Office Online Server, released 2026-09-08
- Severity: High; fixes 5 CVEs, max CVSS 7.8
- Actively exploited (CISA KEV): no
- CVEs include: CVE-2026-81390, CVE-2026-81396, CVE-2026-81401, CVE-2026-81947, CVE-2026-81956
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5002910
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 KB5002910

Released: 2026-09-08
Last changed: 2026-10-16
Changes tracked: 4

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 KB5002910 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5002910 installed? (elevated PowerShell)
Get-HotFix -Id KB5002910 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5002910 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5002910 (checked 2026-10-22). Microsoft lists 1 known issue. Verify against the article before acting.

In Excel Online, the paste operation might fail silently. Although users try to paste content, the source remains selected and the destination is unmodified. When this issue occurs, users receive no indication of the failure, such as a beep or error message.

This issue is fixed in the September 22, 2026, update for Office Online Server (KB4461632) .

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-2026-81396	High	7.8	<1%	No
CVE-2026-81947	High	7.8	<1%	No
CVE-2026-81956	High	7.8	<1%	No
CVE-2026-81390	Medium	5.5	<1%	No
CVE-2026-81401	Medium	5.5	<1%	No

Scope and sources

Affected products

Office Online Server

Also released in September 2026

Authoritative references

Official KB5002910 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.

KB5002910: Office Online Server Security Update (September 2026)

Update summary

Full tracking and change history for KB5002910

Check if KB5002910 is installed

Known issues, from Microsoft

In Excel Online, the paste operation might fail silently. Although users try to paste content, the source remains selected and the destination is unmodified. When this issue occurs, users receive no indication of the failure, such as a beep or error message.

CVEs fixed by this update

Scope and sources

KB5122871

KB5122876

KB5122878

KB5122880

KB5122882

KB5123065

KB5123066

KB5123099