Out-of-bounds read in Microsoft products - CVE-2026-55121

Vulnerability details

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to out-of-bounds read in Microsoft Office when parsing a crafted Office file. A remote attacker can trick the victim into opening a crafted file to disclose sensitive information.

User interaction is required to open a crafted Office file, and the Preview Pane is not an attack vector.

Affected software

How to mitigate CVE-2026-55121

External References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-55121
• https://www.microsoft.com/en-us/microsoft-365/mac/microsoft-365-for-mac?msockid=35f9adb0e74b61392038b90de6fe608c

Related Security Bulletins

• Multiple vulnerabilities in Microsoft Office