Heap-based buffer overflow in Microsoft Office - CVE-2026-123380
Published: November 11, 2026
Vulnerability identifier: #VU165476
CSH Severity: High
CVSS v4: 8.4 [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]
CVE-ID: CVE-2026-123380
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary code with the victim user's privileges.
The vulnerability exists due to a heap-based buffer overflow in Microsoft Office Outlook when an email attachment copied from Outlook is processed by another application. A remote attacker can send a specially crafted email and convince a user to copy its attachment in Outlook for processing by another application to execute arbitrary code with the user's privileges.
The Preview Pane is not an attack vector for this vulnerability.
Affected software
Microsoft Office
How to mitigate CVE-2026-123380
Install security update from vendor's website.
Microsoft Office - addressed in versions 16.0.14334.21048, 16.0.17932.21140