# CVE-2026-81388: Microsoft Excel stack-based buffer overflow

Source: https://junglewise.ai/threats/cve-2026-81388-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-2026-81388 · 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 on the affected system. A malicious Excel file crafted to trigger the overflow could enable an attacker to bypass security controls and gain full control of the system, threatening data confidentiality, integrity, and system availability.

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

## Quick answers

**Is CVE-2026-81388 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-81388 being exploited in the wild.

**How severe is CVE-2026-81388?** 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-2026-81388?** 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-2026-81388 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-81388?** 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 overwrite stack memory with arbitrary data. The vulnerability is triggered by processing a specially crafted Excel file, requiring local execution or user interaction (opening a file). Successful exploitation enables arbitrary code execution in the context of the user running Excel, potentially leading to system compromise. The attack vector is local, and while no active exploitation in the wild has been reported, the high CVSS score (7.8) reflects the severity of code execution capability.

## Affected products

- Microsoft Excel <UNKNOWN>

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81388](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81388)

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