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Microsoft Security Update Guide · SharePoint

Microsoft Office SharePoint Spoofing Vulnerability

Microsoft · EN CVE-2026-102864 Important Action required CVSS 4.6

Published 13 okt 2026

What does this mean?

Spoofing. An attacker can pretend to be another user or source, for example through a misleading link or page.
It can be exploited over the network (including from the internet if the service is reachable there), with an ordinary user account and if a user takes part, for example by opening a link or file.
CVSS 4.6 out of 10: medium. Microsoft rates it Important.
No attacks reported; Microsoft expects exploitation to be less likely.
What should you do? Install the security update for the version you run (or a later cumulative update):
- Microsoft SharePoint Server Subscription Edition: KB5002927 16.0.20326.20190
This applies to SharePoint Server you run yourself. Microsoft updates SharePoint Online in Microsoft 365.

Microsoft Office SharePoint · Spoofing

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.

SharePoint Office / Microsoft 365 Apps

How do I check if I am affected?

SharePoint Server: check and update

Check your farm build in the SharePoint Management Shell:
```
(Get-SPFarm).BuildVersion
```
Or in Central Administration → Upgrade and Migration → Check product and patch installation status.
If the build is equal to or higher than the build under "Affected products and updates" below, this vulnerability is fixed. A later cumulative update includes the fix too.

Otherwise install the update on every server in the farm, then run the SharePoint Products Configuration Wizard, or:

PSConfig.exe -cmd upgrade -inplace b2b -wait -cmd applicationcontent -install -cmd installfeatures -cmd secureresources -cmd services -install

You do not need to update SharePoint Online in Microsoft 365; Microsoft does that.

What kind of flaw is this?

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Input is not cleaned before it appears in a web page (cross-site scripting). An attacker can run script in another user's browser.

Key facts

Released

13 okt 2026

Impact

Spoofing

Max severity

Important

Weakness

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS 3.1

4.6 / 4.0 (base / temporal)

Vector string

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C

Publicly disclosed

Exploited

Exploitability assessment

Exploitation Less Likely

Customer action required

Yes

Links

Microsoft Security Update Guide · CVE.org

CVSS metrics

Base score metrics
Attack Vector	Network
Attack Complexity	Low
Privileges Required	Low
User Interaction	Required
Scope	Unchanged
Confidentiality	Low
Integrity	Low
Availability	None
Temporal score metrics
Exploit Code Maturity	Unproven
Remediation Level	Official Fix
Report Confidence	Confirmed

Affected products and updates

Product	Update	Build
Microsoft SharePoint Server Subscription Edition	KB5002927 · Security Update	`16.0.20326.20190`

FAQ

Is the Preview Pane an attack vector for this vulnerability?: No, the Preview Pane is not an attack vector.

Revisions

Version	Date	Note
1	13 okt 2026	Information published.

This is in the weekly digest for week 42: everything that changed in Microsoft 365 this week. →

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Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.