# CVE-2026-40362: Microsoft Office Excel heap buffer overflow

Source: https://junglewise.ai/threats/cve-2026-40362-microsoft-office-excel-heap-buffer-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-12. Updated: 2026-05-19  
License: CC BY 4.0 with a link back

CVE-2026-40362 · Severity: high · CVSS 7.8 · Published 2026-05-12

A security vulnerability exists in Microsoft Excel, the widely used spreadsheet application. If a user opens a specially crafted malicious file, an attacker could gain the ability to run unauthorized commands or software on the victim's computer. This could lead to a full system compromise, data theft, or the installation of malware.

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

## Quick answers

**Is CVE-2026-40362 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40362 being exploited in the wild.

**How severe is CVE-2026-40362?** High severity, with a CVSS score of 7.8, published 12 May 2026.

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

**Is there a fix for CVE-2026-40362?** 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-2026-40362 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-40362?** Check whether you run Microsoft Excel. 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 within Microsoft Office Excel. The flaw is triggered when the application fails to properly validate or bounds-check data while processing a specially crafted Excel file. An attacker can exploit this by tricking a user into opening a malicious document, leading to arbitrary code execution in the context of the current user. The attack vector is local, requiring user interaction (UI:R), and carries a CVSS base score of 7.8 due to the high impact on confidentiality, integrity, and availability.

## Affected products

- Microsoft Office Excel

## Timeline

- 2026-05-12: disclosed
- 2026-05-12: advisory: Published by Microsoft and NVD

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40362](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40362)

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