CVE-2026-55048: Microsoft Excel integer overflow local code execution

CVE-2026-55048 · Severity: high · CVSS 7.8 · Published 2026-07-14

Microsoft Excel is affected by a security vulnerability that could allow an attacker to run malicious code on a user's computer. This typically occurs if a user is tricked into opening a specially crafted Excel file. If successful, an attacker could gain the same permissions as the local user, potentially leading to data theft, unauthorized system changes, or further malware installation.

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-2026-55048 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55048 being exploited in the wild.
How severe is CVE-2026-55048?
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 < 16.0.5561.1001; Microsoft Office 2019 < 19.0.0 (see aka.ms/OfficeSecurityReleases); Microsoft Office 365 for Mac < 16.111.26071215; and 5 more.
Is there a fix for CVE-2026-55048?
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-2026-55048 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55048?
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 classified as an integer overflow or wraparound (CWE-190) which leads to a heap-based buffer overflow (CWE-122) within Microsoft Excel. The attack vector is local, requiring a user to interact with a malicious file (User Interaction: Required). Successful exploitation allows an unauthorized attacker to execute arbitrary code in the context of the current user. The vulnerability affects multiple versions of Microsoft Office, including Office 2016, 2019, LTSC 2021/2024, and Microsoft 365 Apps on both Windows and macOS platforms. Microsoft has released security updates to address this issue.

Affected products

  • Microsoft Microsoft 365 Apps for Enterprise < 16.0.1 (see aka.ms/OfficeSecurityReleases)
  • Microsoft Microsoft Excel 2016 < 16.0.5561.1001
  • Microsoft Microsoft Office 2019 < 19.0.0 (see aka.ms/OfficeSecurityReleases)
  • Microsoft Microsoft Office 365 for Mac < 16.111.26071215
  • Microsoft Microsoft Office LTSC 2021 < 16.0.1 (see aka.ms/OfficeSecurityReleases)
  • Microsoft Microsoft Office LTSC 2024 < 16.0.0 (see aka.ms/OfficeSecurityReleases)
  • 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
  • 2026-07-14: patched: Security updates made available via Microsoft Update Guide

References

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