CVE-2026-55041: Microsoft Excel heap buffer overflow code execution

CVE-2026-55041 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Excel that could allow an attacker to take control of a user's computer. This occurs when a user is tricked into opening a specially crafted, malicious Excel file. If successful, the attacker could gain the same permissions as the current user, potentially leading to data theft or the installation of unauthorized software.

Technologies: Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019, Microsoft Office 365 for Mac, Microsoft Office LTSC 2021, Microsoft Office LTSC 2024, Microsoft Office LTSC for Mac 2021, Microsoft Office LTSC for Mac 2024, Microsoft Office Online Server. Vendors: Microsoft.

Quick answers

Is CVE-2026-55041 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55041 being exploited in the wild.
How severe is CVE-2026-55041?
High severity, with a CVSS score of 7.8, published 14 July 2026.
Which products and versions are affected?
Microsoft 365 Apps for Enterprise < 16.0.1 (See aka.ms/OfficeSecurityReleases); Microsoft Excel 2016 16.0.0.0 to < 16.0.5561.1001; Microsoft Office 2019 < 19.0.0 (See aka.ms/OfficeSecurityReleases); Microsoft Office 365 for Mac 1.0.0 to < 16.111.26071215; and 5 more.
Is there a fix for CVE-2026-55041?
A patch was published on 2026-07-14: Security updates made available via Microsoft Update Guide. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55041 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55041?
Check whether you run Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A heap-based buffer overflow vulnerability (CWE-122) exists in Microsoft Office Excel across multiple versions, including Office 2019, 2021, 2024, and Microsoft 365 Apps. The vulnerability is triggered when the application fails to properly validate input while processing a specially crafted Excel file. An attacker can exploit this by convincing a user to open a malicious file, leading to arbitrary code execution in the context of the current user. The attack vector is local, requiring user interaction (UI:R), but does not require prior administrative privileges (PR:N). Microsoft has released security updates to address this issue.

Affected products

  • Microsoft 365 Apps for Enterprise < 16.0.1 (See aka.ms/OfficeSecurityReleases)
  • Microsoft Excel 2016 16.0.0.0 to < 16.0.5561.1001
  • Microsoft Office 2019 < 19.0.0 (See aka.ms/OfficeSecurityReleases)
  • Microsoft Office 365 for Mac 1.0.0 to < 16.111.26071215
  • Microsoft Office LTSC 2021 < 16.0.1 (See aka.ms/OfficeSecurityReleases)
  • Microsoft Office LTSC 2024 < 16.0.0 (See aka.ms/OfficeSecurityReleases)
  • Microsoft Office LTSC for Mac 2021 < 16.0.1 (See aka.ms/OfficeSecurityReleases)
  • Microsoft Office LTSC for Mac 2024 < 16.0.0 (See aka.ms/OfficeSecurityReleases)
  • Microsoft Office Online Server 16.0.0.0 to < 16.0.10417.20175

Timeline

  • 2026-07-14: advisory: Initial advisory published by Microsoft and NVD.
  • 2026-07-14: patched: Security updates made available via Microsoft Update Guide.

References

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