# CVE-2026-44820: Microsoft Office Excel integer underflow code execution

Source: https://junglewise.ai/threats/cve-2026-44820-microsoft-office-excel-integer-underflow-code-execution  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-09. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-44820 · Severity: high · CVSS 7.8 · Published 2026-06-09

Microsoft Excel, a widely used spreadsheet application, contains a security vulnerability that could allow an attacker to run malicious code on a user's computer. To exploit this, an attacker would typically need to trick a user into opening a specially crafted Excel file. Successful exploitation could lead to a full system compromise, allowing the attacker to steal data, install software, or disrupt business operations.

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

## Quick answers

**Is CVE-2026-44820 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-44820 being exploited in the wild.

**How severe is CVE-2026-44820?** High severity, with a CVSS score of 7.8, published 9 June 2026.

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

**Is there a fix for CVE-2026-44820?** 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-2026-44820 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-44820?** 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

An integer underflow (wraparound) vulnerability exists in Microsoft Office Excel, which can lead to an out-of-bounds memory access (CWE-125). The vulnerability is triggered when the application processes a malformed Excel file. An attacker can exploit this by convincing a user to open a malicious document, leading to arbitrary code execution in the context of the current user. The attack vector is local with a requirement for user interaction (UI:R), and it carries a high impact on confidentiality, integrity, and availability. Microsoft has released security updates to address this issue.

## Affected products

- Microsoft Excel

## Timeline

- 2026-06-09: disclosed
- 2026-06-09: advisory: Published by Microsoft and NVD

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820)

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