CVE-2026-55141: Microsoft Office Excel stack-based buffer overflow

CVE-2026-55141 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability exists in Microsoft Excel that could allow an attacker to take control of a user's computer. To exploit this, an attacker would typically need to trick a user into opening a specially crafted malicious Excel file. Successful exploitation could lead to the unauthorized installation of programs, data theft, or full system compromise.

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 Online Server. Vendors: Microsoft.

Quick answers

Is CVE-2026-55141 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55141 being exploited in the wild.
How severe is CVE-2026-55141?
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 3 more.
Is there a fix for CVE-2026-55141?
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-2026-55141 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55141?
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 stack-based buffer overflow (CWE-121) exists in Microsoft Office Excel due to improper validation of user-supplied data when parsing Excel files. The vulnerability is triggered when a user opens a specially crafted file, leading to memory corruption. An attacker can exploit this to execute arbitrary code in the context of the current user. The attack vector is local, requiring user interaction (UI:R) to open the malicious document. Microsoft has released security updates for various versions of Office, including Excel 2016, 2019, LTSC 2021/2024, and Microsoft 365 Apps.

Affected products

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

Timeline

  • 2026-07-14: disclosed: Initial publication of CVE-2026-55141 by Microsoft.

References

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