CVE-2026-55053: Microsoft Excel heap buffer overflow code execution

CVE-2026-55053 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Excel, the widely used spreadsheet application. An attacker could exploit this flaw by tricking a user into opening a specially crafted file, potentially allowing the attacker to take control of the user's computer. This could lead to the theft of sensitive data, unauthorized changes to files, or a complete disruption of business operations on the affected machine.

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-2026-55053 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55053 being exploited in the wild.
How severe is CVE-2026-55053?
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 to latest security release; Microsoft Excel 2016 16.0.0.0 to 16.0.5561.1001; Microsoft Office 2019 19.0.0 to latest security release; Microsoft Office 365 for Mac 1.0.0 to 16.111.26071215; and 5 more.
Is there a fix for CVE-2026-55053?
A patch was published on 2026-07-14: Security updates made available via the Microsoft Update Guide. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55053 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55053?
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

This vulnerability is a heap-based buffer overflow (CWE-122) within Microsoft Excel. The flaw is triggered when the application processes a specially crafted file, leading to memory corruption. While the attack vector is classified as local, it requires user interaction (UI:R), typically involving a victim opening a malicious spreadsheet provided by the attacker. Successful exploitation allows for arbitrary code execution in the context of the current user. Microsoft has released security updates to address this issue across various versions of Office, including LTSC and Microsoft 365 Apps.

Affected products

  • Microsoft Microsoft 365 Apps for Enterprise 16.0.1 to latest security release
  • Microsoft Microsoft Excel 2016 16.0.0.0 to 16.0.5561.1001
  • Microsoft Microsoft Office 2019 19.0.0 to latest security release
  • Microsoft Microsoft Office 365 for Mac 1.0.0 to 16.111.26071215
  • Microsoft Microsoft Office LTSC 2021 16.0.1 to latest security release
  • Microsoft Microsoft Office LTSC 2024 16.0.0 to latest security release
  • Microsoft Microsoft Office LTSC for Mac 2021 16.0.1 to 16.111.26071215
  • Microsoft Microsoft Office LTSC for Mac 2024 16.0.0 to 16.111.26071215
  • Microsoft Office Online Server 16.0.0.0 to 16.0.10417.20175

Timeline

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

References

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