# CVE-2026-124229: Microsoft Office Excel unsafe deserialization in file parsing

Source: https://junglewise.ai/threats/cve-2026-124229-deserialization-of-untrusted-data-in-microsoft-office-excel  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-124229 · Severity: medium · CVSS 6.6 · Published 2026-11-10

Microsoft Office Excel contains a vulnerability in how it processes files, allowing an attacker with physical access to a computer to execute arbitrary code by crafting a malicious spreadsheet. This could lead to unauthorized access, data theft, or system compromise when a user opens a specially prepared Excel file.

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

## Quick answers

**Is CVE-2026-124229 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-124229 being exploited in the wild.

**How severe is CVE-2026-124229?** Medium severity, with a CVSS score of 6.6, published 10 November 2026.

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

**Is there a fix for CVE-2026-124229?** 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-2026-124229 attacked?** It is attacked with physical access or with local access.

**Am I affected by CVE-2026-124229?** Check whether you run Microsoft Office 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

The vulnerability exists in Excel's deserialization of untrusted data during file parsing. An attacker can exploit this via a specially crafted Excel file to achieve code execution with the privileges of the user opening the file. Exploitation requires physical or local access to deliver the malicious file to the target system.

## Affected products

- Microsoft Office Excel

## Timeline

- 2026-11-10: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-124229](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-124229)

## Related threats

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- [Microsoft Office Excel out-of-bounds read](https://junglewise.ai/threats/cve-2026-124178-out-of-bounds-read-in-microsoft-office-excel-allows-an)
- [Microsoft Office Excel heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-124176-heap-based-buffer-overflow-in-microsoft-office-excel-allows-an)