#VU121285 Integer underflow in Microsoft products - CVE-2026-20957
Published: January 13, 2026
Vulnerability identifier: #VU121285
Vulnerability risk: High
CVSSv4.0: 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-2026-20957
CWE-ID: CWE-191
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Office Online Server
Microsoft Office
Microsoft Excel
Microsoft 365 Apps for Enterprise
Microsoft Office LTSC
Office Online Server
Microsoft Office
Microsoft Excel
Microsoft 365 Apps for Enterprise
Microsoft Office LTSC
Software vendor:
Microsoft
Microsoft
Description
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to integer underflow in Microsoft Excel. A remote attacker can trick a victim to open a specially crafted file, trigger integer underflow and execute arbitrary code on the target system.
Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
Remediation
Install updates from vendor's website.