Stack-based buffer overflow in Microsoft Office - CVE-2026-123385

Vulnerability details

The vulnerability allows a remote attacker to execute arbitrary code with the victim user's privileges.

The vulnerability exists due to a stack-based buffer overflow in Microsoft Office Excel when processing a specially crafted workbook. A remote attacker can send such a workbook and convince a user to open it, enable editing, and allow its accompanying content to load to execute arbitrary code with that user's privileges.

The Preview Pane is not an attack vector for this vulnerability.

Affected software

How to mitigate CVE-2026-123385

External References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-123385
• https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates

Related Security Bulletins

• Multiple vulnerabilities in Microsoft Office