Heap-based buffer overflow in Microsoft products - CVE-2026-81959

Vulnerability details

The vulnerability allows a remote attacker to execute arbitrary code locally.

The vulnerability exists due to a heap-based buffer overflow in Microsoft Excel when opening a crafted Office file. A remote attacker can send a malicious Office file and convince a victim to open it to execute arbitrary code locally.

The Preview Pane is not an attack vector.

Affected software

How to mitigate CVE-2026-81959

External References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-81959
• https://support.microsoft.com/help/5002910

Related Security Bulletins

• Multiple vulnerabilities in Microsoft Office