CVE-2026-55018: Microsoft Office use after free local code execution

CVE-2026-55018 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Office, the widely used suite of productivity applications. If exploited, this flaw could allow an attacker to execute malicious code on a user's computer, potentially leading to full system compromise or data theft. The attack requires a user to open a specially crafted file, making it a significant risk for phishing or targeted social engineering campaigns.

Technologies: Microsoft 365 Apps for Enterprise, Microsoft Office 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. Vendors: Microsoft.

Quick answers

Is CVE-2026-55018 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55018 being exploited in the wild.
How severe is CVE-2026-55018?
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 up to security releases; Microsoft Office 2016 16.0.0 to 16.0.5561.1000; Microsoft Office 2019 19.0.0 up to security releases; Microsoft Office 365 for Mac 1.0.0 to 16.111.26071215; and 4 more.
Is there a fix for CVE-2026-55018?
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-2026-55018 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55018?
Check whether you run Microsoft 365 Apps for Enterprise, Microsoft Office 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 a Use-After-Free (CWE-416) within Microsoft Office. The flaw is triggered when the application attempts to access memory that has already been freed, which can be exploited to achieve local code execution. The attack vector is local, but it requires user interaction (UI:R), typically involving a victim opening a malicious document. The vulnerability affects multiple versions of Office across both Windows and macOS platforms. Microsoft has released security updates to address this issue, and users are advised to apply the latest patches for their specific Office version.

Affected products

  • Microsoft Microsoft 365 Apps for Enterprise 16.0.1 up to security releases
  • Microsoft Microsoft Office 2016 16.0.0 to 16.0.5561.1000
  • Microsoft Microsoft Office 2019 19.0.0 up to security releases
  • Microsoft Microsoft Office 365 for Mac 1.0.0 to 16.111.26071215
  • Microsoft Microsoft Office LTSC 2021 16.0.1 up to security releases
  • Microsoft Microsoft Office LTSC 2024 16.0.0 up to security releases
  • 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

Timeline

  • 2026-07-14: disclosed
  • 2026-07-14: advisory

References

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