# CVE-2026-55017: Microsoft Office heap overflow code execution

Source: https://junglewise.ai/threats/cve-2026-55017-microsoft-office-heap-overflow-code-execution  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-55017 · Severity: high · CVSS 7.8 · Published 2026-07-14

Microsoft Office, a widely used suite of productivity applications, is affected by a security vulnerability that could allow an attacker to take control of a user's computer. To exploit this, an attacker would typically need to trick a user into opening a specially crafted file. Successful exploitation could lead to unauthorized access to sensitive data, installation of malicious software, or disruption of business operations.

Technologies: [Microsoft 365 Apps for Enterprise](https://junglewise.ai/threats/technologies/365-apps-for-enterprise), [Microsoft Office 2016](https://junglewise.ai/threats/technologies/office-2016), [Microsoft Office 2019](https://junglewise.ai/threats/technologies/office-2019), [Microsoft Office LTSC 2021](https://junglewise.ai/threats/technologies/office-ltsc-2021), [Microsoft Office LTSC 2024](https://junglewise.ai/threats/technologies/office-ltsc-2024). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-55017 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55017 being exploited in the wild.

**How severe is CVE-2026-55017?** 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 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 LTSC 2021 16.0.1 to latest security release; and 1 more.

**Is there a fix for CVE-2026-55017?** 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-2026-55017 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-55017?** 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

A heap-based buffer overflow vulnerability (CWE-122) exists in multiple versions of Microsoft Office, including Office 2016, 2019, LTSC 2021, LTSC 2024, and Microsoft 365 Apps. The vulnerability is triggered when the application fails to properly validate input, leading to memory corruption. An attacker can exploit this by convincing a user to open a malicious file, resulting in arbitrary code execution in the context of the current user. The attack vector is local, but requires user interaction (UI:R). Microsoft has released security updates to address this issue.

## 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 LTSC 2021 16.0.1 to latest security release
- Microsoft Microsoft Office LTSC 2024 16.0.0 to latest security release

## Timeline

- 2026-07-14: advisory: Initial disclosure by Microsoft and NVD publication.
- 2026-07-14: patched: Security updates made available via Microsoft Update Guide.

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55017](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55017)

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- [Microsoft Office out-of-bounds read information disclosure](https://junglewise.ai/threats/cve-2026-56195-microsoft-office-out-of-bounds-read-information-disclosure)
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- [Microsoft Office Excel heap buffer overflow](https://junglewise.ai/threats/cve-2026-56156-microsoft-office-excel-heap-buffer-overflow)
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