# CVE-2026-81396: Microsoft Excel stack-based buffer overflow

Source: https://junglewise.ai/threats/cve-2026-81396-microsoft-excel-stack-based-buffer-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-08. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-81396 · Severity: high · CVSS 7.8 · Published 2026-09-08

Microsoft Excel contains a stack-based buffer overflow vulnerability that allows an attacker with local access to execute arbitrary code with user privileges. Exploitation requires the attacker to craft a malicious Excel file and have it opened by a user, potentially leading to system compromise, data theft, or malware installation.

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

## Quick answers

**Is CVE-2026-81396 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-81396 being exploited in the wild.

**How severe is CVE-2026-81396?** High severity, with a CVSS score of 7.8, published 8 September 2026.

**Which products and versions are affected?** Microsoft Excel <UNKNOWN>.

**Is there a fix for CVE-2026-81396?** 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-2026-81396 attacked?** It is attacked with local access, in a web application.

**Am I affected by CVE-2026-81396?** Check whether you run Microsoft Excel 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 stack-based buffer overflow exists in Microsoft Excel's file parsing logic, allowing an attacker to write beyond the boundaries of a stack-allocated buffer. The vulnerability requires local code execution context and user interaction (opening a malicious .xls or related file format). An attacker can exploit this by crafting a specially formatted Excel document that triggers the overflow when processed, achieving arbitrary code execution in the context of the user running Excel. A patch is expected to be available through Microsoft Security Updates.

## Affected products

- Microsoft Excel <UNKNOWN>

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81396](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81396)

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