# CVE-2026-66807: Microsoft Office stack-based buffer overflow

Source: https://junglewise.ai/threats/cve-2026-66807-microsoft-office-stack-based-buffer-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-11. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-66807 · Severity: high · CVSS 7.8 · Published 2026-08-11

Microsoft Office is a widely-used productivity suite for creating and editing documents, spreadsheets, and presentations. A stack-based buffer overflow vulnerability allows an attacker to execute malicious code on a user's computer, potentially leading to data theft, system compromise, or installation of malware.

Technologies: [Microsoft Office](https://junglewise.ai/threats/technologies/office). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-66807 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-66807 being exploited in the wild.

**How severe is CVE-2026-66807?** High severity, with a CVSS score of 7.8, published 11 August 2026.

**Which products and versions are affected?** Microsoft Office.

**Is there a fix for CVE-2026-66807?** 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-2026-66807 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-66807?** Check whether you run Microsoft Office. 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 exists in Microsoft Office that can be exploited to execute arbitrary code with local privilege context. The vulnerability is triggered during document parsing or processing. An attacker must first trick a user into opening a specially crafted Office document to trigger the overflow. Once exploited, the attacker gains code execution on the affected system, allowing them to read/modify files, install malware, or pivot to other systems on the network. Microsoft has released patches to address this issue.

## Affected products

- Microsoft Office

## Timeline

- 2026-08-11: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66807](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66807)

## Related threats

- [Microsoft Office Outlook user warning spoofing vulnerability](https://junglewise.ai/threats/cve-2026-124194-microsoft-office-outlook-missing-user-interaction-for)
- [Microsoft Office heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-122198-heap-based-buffer-overflow-in-microsoft-office-allows-an)
- [Microsoft Office heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-120003-heap-based-buffer-overflow-in-microsoft-office-allows-an)
- [Microsoft Office UI security feature bypass](https://junglewise.ai/threats/cve-2026-119998-product-ui-does-not-warn-user-of-unsafe-actions-in-microsoft)
- [Microsoft Office heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-116717-heap-based-buffer-overflow-in-microsoft-office-allows-an)