Microsoft Security Update Guide · SharePoint
Microsoft Office SharePoint Tampering Vulnerability
Published
What does this mean?
- Tampering. An attacker can change data or settings without permission.
- It can be exploited over the network (including from the internet if the service is reachable there), with an ordinary user account and without any user action.
- CVSS 6.8 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
- This applies to SharePoint Server you run yourself. Microsoft updates SharePoint Online in Microsoft 365.
Observable discrepancy in Microsoft Office SharePoint allows an authorized attacker to perform tampering 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:
Or in Central Administration → Upgrade and Migration → Check product and patch installation status.(Get-SPFarm).BuildVersion - 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.
Key facts
Released
13 okt 2026
Impact
Tampering
Max severity
Important
Weakness
CVSS 3.1
6.8 / 5.9 (base / temporal)
Vector string
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:CPublicly disclosed
No
Exploited
No
Exploitability assessment
Exploitation Less Likely
Customer action required
Yes
Links
CVSS metrics
| Base score metrics | |
|---|---|
| Attack Vector | Network |
| Attack Complexity | High |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity | High |
| 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 | — | — |
FAQ
- How could an attacker exploit this vulnerability?
- An authenticated attacker with access to an affected SharePoint form could submit specially crafted session data to the server. Successful exploitation could allow the attacker to alter trusted application state and cause unauthorized backend actions; user interaction is not required.
- According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
- Successful exploitation of this vulnerability requires an attacker to have a deep understanding of the system and the ability to manipulate its components to trigger a specific condition. Successful exploitation is not guaranteed and depends on a combination of factors that may include the environment, system configuration, and the presence of additional security measures.
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. →
View at Microsoft → ← All security advisories
Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.
