CVE-2026-55039

Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

Score

CVSS 3.1 7.8 High

Status

Analyzed - secure@microsoft.com

Published

2026-07-14

Last modified

2026-10-28

Weaknesses

CWE-122, CWE-191

Affected products

• 365 Apps (Microsoft)
• Excel (Microsoft)
• Excel 2016 (Microsoft)
• Microsoft 365 (Microsoft)
• Office 2019 (Microsoft)
• Office 2021 (Microsoft)
• Office 2024 (Microsoft)
• Office 365 (Microsoft)
• Office Macos 2021 (Microsoft)
• Office Macos 2024 (Microsoft)
• Office Online Server (Microsoft)

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55039