CVE-2026-55134: Microsoft Office Word stack-based buffer overflow

CVE-2026-55134 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Word, the widely used word processing application. An attacker could exploit this flaw to execute malicious code on a user's computer if the user is tricked into opening a specially crafted file. This could lead to a full system compromise, allowing the attacker to steal data, install programs, or disrupt business operations.

Technologies: Microsoft SharePoint Server, Microsoft Word. Vendors: Microsoft.

Quick answers

Is CVE-2026-55134 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55134 being exploited in the wild.
How severe is CVE-2026-55134?
High severity, with a CVSS score of 7.8, published 14 July 2026.
Which products and versions are affected?
Microsoft Word Microsoft 365 Apps, Office 2019, Office LTSC 2021/2024, Office for Mac, SharePoint Server.
Is there a fix for CVE-2026-55134?
A patch was published on 2026-07-14: Security updates made available via MSRC Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55134 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55134?
Check whether you run Microsoft SharePoint Server or Microsoft Word 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 Word. The vulnerability is triggered when the application fails to properly validate input while parsing a document, leading to memory corruption. An attacker can exploit this by convincing a user to open a specially crafted file (User Interaction required). Successful exploitation allows for arbitrary code execution in the context of the current user. The vulnerability affects multiple versions of Office, including Microsoft 365 Apps, Office LTSC, and SharePoint Server. Microsoft has released security updates to address this issue.

Affected products

  • Microsoft Office Word Microsoft 365 Apps, Office 2019, Office LTSC 2021/2024, Office for Mac, SharePoint Server

Timeline

  • 2026-07-14: advisory: Initial publication by Microsoft and NVD
  • 2026-07-14: patched: Security updates made available via MSRC

References

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