Heap-based buffer overflow in Microsoft Office for macOS and Microsoft Office - CVE-2026-108439

Vulnerability details

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

The vulnerability exists due to a heap-based buffer overflow in Microsoft Office Word when processing RTF files. A remote attacker can trick a user into opening a malicious RTF file or viewing it in the Preview Pane to execute arbitrary code in the user's context.

Affected software

How to mitigate CVE-2026-108439

External References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-108439
• https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates

Related Security Bulletins

• Multiple vulnerabilities in Microsoft Office