Heap-based buffer overflow in Microsoft Office - CVE-2026-123384
Published: November 11, 2026
Vulnerability identifier: #VU165480
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-2026-123384
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 on the client system.
The vulnerability exists due to a heap-based buffer overflow in Microsoft Office Outlook when processing a malicious server's response. A remote attacker can host a malicious server and convince a user to connect to it from an affected client to execute arbitrary code on the client system.
The Preview Pane is not an attack vector for this vulnerability.
Affected software
Microsoft Office
How to mitigate CVE-2026-123384
Install security update from vendor's website.
Microsoft Office - addressed in versions 16.0.14334.21048, 16.0.17932.21140