CVE-2026-55057: Microsoft Office integer overflow information disclosure

CVE-2026-55057 · Severity: medium · CVSS 5.5 · Published 2026-07-14

A vulnerability in Microsoft Office could allow an attacker to access sensitive information on a user's computer. To exploit this, an attacker would typically need to trick a user into opening a specially crafted file. This could lead to the unauthorized disclosure of private data stored in the system's memory.

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-2026-55057 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55057 being exploited in the wild.
How severe is CVE-2026-55057?
Medium severity, with a CVSS score of 5.5, published 14 July 2026.
Which products and versions are affected?
Microsoft 365 Apps for Enterprise 16.0.1 to latest security release; Microsoft Office 2016 16.0.0 to 16.0.5561.1000; Microsoft Office 2019 19.0.0 to latest security release; Microsoft Office 365 for Mac 1.0.0 to 16.111.26071215; and 4 more.
Is there a fix for CVE-2026-55057?
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-2026-55057 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55057?
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

An integer overflow or wraparound vulnerability (CWE-190) exists in multiple versions of Microsoft Office, including Office 2016, 2019, 2021, 2024, and Microsoft 365 Apps. The flaw is triggered when the application processes a specially crafted file, leading to an out-of-bounds memory read. An attacker can exploit this locally by convincing a user to open a malicious document (User Interaction required). Successful exploitation allows the attacker to disclose sensitive information from the process memory. Microsoft has released security updates to address this issue across affected platforms.

Affected products

  • Microsoft Microsoft 365 Apps for Enterprise 16.0.1 to latest security release
  • Microsoft Microsoft Office 2016 16.0.0 to 16.0.5561.1000
  • 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

Timeline

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

References

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