CVE-2026-109454: Microsoft Office SharePoint Spoofing Vulnerability
CVE-2026-109454 is a spoofing vulnerability in Microsoft Office SharePoint, rated Important by Microsoft, with a CVSS 3.1 base score of 9 (Critical). An attacker can exploit it remotely over the network, with low privileges and only if a user takes an action. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. Microsoft released the fix on 10 November 2026 in the November 2026 Patch Tuesday, delivered through 1 security update (KB5002945). It affects 1 product in 1 product family (Microsoft Office).
Key facts
- CVE ID
- CVE-2026-109454
- Severity
- Critical CVSS 9
- Microsoft severity
- Important
- Impact
- Spoofing
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- November 2026 Patch Tuesday
- Product families
- Microsoft Office
CVSS score and vector
Microsoft scores CVE-2026-109454 at 9 (temporal 7.8) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | Low |
| User interaction | Required |
| Scope | Changed |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
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.
Frequently asked questions (Microsoft)
How could an attacker exploit this vulnerability?
An authenticated attacker with permissions to add or modify content on an affected SharePoint page could store malicious script content in the page. The script could run in the security context of another user when that user views and interacts with the affected content, potentially allowing the attacker to access or modify SharePoint data available to that user.
Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.
Affected products (1)
Microsoft Office
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Microsoft SharePoint Server Subscription Edition | KB5002945 | Security Update | 16.0.20326.20278 |
Security updates (1)
- KB5002945 (Security Update)
Acknowledgments
- P1hcn
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |