CVE-2026-55136: Microsoft Excel untrusted pointer dereference remote code execution

CVE-2026-55136 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Excel 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 exploited, an attacker could gain the same permissions as the local user, potentially leading to data theft, unauthorized system changes, or the installation of malware.

Technologies: Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019, Microsoft Office LTSC 2021, Microsoft Office LTSC 2024, Microsoft Office Online Server. Vendors: Microsoft.

Quick answers

Is CVE-2026-55136 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55136 being exploited in the wild.
How severe is CVE-2026-55136?
High severity, with a CVSS score of 7.8, published 14 July 2026.
Which products and versions are affected?
Microsoft 365 Apps for Enterprise All versions; Microsoft Excel 2016 < 16.0.5561.1001; Microsoft Office 2019 All versions; Microsoft Office LTSC 2021 All versions; and 2 more.
Is there a fix for CVE-2026-55136?
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-2026-55136 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-55136?
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 vulnerability classified as an untrusted pointer dereference (CWE-822) exists in Microsoft Excel. The flaw is triggered when the application processes a specially crafted file containing malicious pointer data that the application fails to properly validate before dereferencing. An attacker can exploit this by convincing a user to open a malicious spreadsheet, leading to arbitrary code execution in the context of the current user. The vulnerability affects multiple versions of Microsoft Office across Windows and macOS, including Office 2016, 2019, LTSC 2021/2024, and Microsoft 365 Apps. Microsoft has released security updates to address this issue.

Affected products

  • Microsoft Excel 2016 < 16.0.5561.1001
  • Microsoft Office 2019 All versions
  • Microsoft Office LTSC 2021 All versions
  • Microsoft Office LTSC 2024 All versions
  • Microsoft Microsoft 365 Apps for Enterprise All versions
  • Microsoft Office Online Server < 16.0.10417.20175
  • Microsoft Office for Mac (365, LTSC 2021, LTSC 2024) < 16.111.26071215

Timeline

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

References

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