CVE-2026-55044: Microsoft Office Excel out-of-bounds read code execution

CVE-2026-55044 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Excel, the widely used spreadsheet application. If a user is tricked into opening a specially crafted malicious file, an attacker could gain the ability to run unauthorized code on the user's computer. This could lead to the theft of sensitive data, system instability, or full control over the affected workstation.

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-2026-55044 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55044 being exploited in the wild.
How severe is CVE-2026-55044?
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; Microsoft Excel 2016 < 16.0.5561.1001; Microsoft Office 2019 < 19.0.0; Microsoft Office 365 for Mac < 16.111.26071215; and 5 more.
Is there a fix for CVE-2026-55044?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-55044 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55044?
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

An out-of-bounds read vulnerability (CWE-125) exists in Microsoft Office Excel due to improper validation of input data when parsing spreadsheet files. The attack vector is local, requiring a user to open a specially crafted file (User Interaction required). Successful exploitation allows an attacker to bypass memory protections and achieve arbitrary code execution in the context of the current user. Microsoft has released security updates for affected versions including Excel 2016, Office 2019, LTSC versions, and Microsoft 365 Apps.

Affected products

  • Microsoft Microsoft 365 Apps for Enterprise < 16.0.1
  • Microsoft Microsoft Excel 2016 < 16.0.5561.1001
  • Microsoft Microsoft Office 2019 < 19.0.0
  • Microsoft Microsoft Office 365 for Mac < 16.111.26071215
  • Microsoft Microsoft Office LTSC 2021 < 16.0.1
  • Microsoft Microsoft Office LTSC 2024 < 16.0.0
  • Microsoft Microsoft Office LTSC for Mac 2021 < 16.111.26071215
  • Microsoft Microsoft Office LTSC for Mac 2024 < 16.111.26071215
  • Microsoft Office Online Server < 16.0.10417.20175

Timeline

  • 2026-07-14: advisory: Initial publication by Microsoft and NVD

References

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