Improper access control in Microsoft Office LTSC and Microsoft 365 Apps for Enterprise - CVE-2026-20949
Published: January 13, 2026
Vulnerability identifier: #VU121289
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-20949
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Microsoft
Affected software:
Microsoft Office LTSC
Microsoft 365 Apps for Enterprise
Microsoft Office LTSC
Microsoft 365 Apps for Enterprise
Detailed vulnerability description
The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.
The vulnerability exists due to improper access restrictions in Microsoft Excel. A remote attacker can trick a victim to open the malicious workbook, enable editing and then click the attacker‑supplied Quick Access Toolbar (QAT) button to bypass a security feature.
How to mitigate CVE-2026-20949
Install updates from vendor's website.