Heap-based buffer overflow in Microsoft Office - CVE-2026-123377
Published: November 11, 2026
Vulnerability identifier: #VU165473
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-2026-123377
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 processing a crafted contact file while viewing the contact's certificates. A remote attacker can send a specially crafted contact file and convince a user to open it in Outlook and view the contact's certificates to execute arbitrary code with that user's privileges.
The Preview Pane is not an attack vector for this vulnerability.
Affected software
Microsoft Office
How to mitigate CVE-2026-123377
Install security update from vendor's website.
Microsoft Office - addressed in versions 16.0.14334.21048, 16.0.17932.21140