# CVE-2026-100212: Microsoft Office Excel use-after-free remote code execution

Source: https://junglewise.ai/threats/cve-2026-100212-use-after-free-in-microsoft-office-excel-allows-an-unauthorized  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-100212 · Severity: high · CVSS 8.8 · Published 2026-10-13

Microsoft Office Excel contains a use-after-free vulnerability that allows an attacker to execute arbitrary code on a user's computer over the network. An attacker could exploit this by sending a specially crafted Excel file that, when opened, executes malicious code with the privileges of the user running Excel. This could lead to data theft, system compromise, or ransomware installation.

Technologies: [Microsoft 365 Apps](https://junglewise.ai/threats/technologies/365-apps), [Microsoft 365](https://junglewise.ai/threats/technologies/microsoft-365), [Microsoft Office 2021](https://junglewise.ai/threats/technologies/office-2021), [Microsoft Office 2024](https://junglewise.ai/threats/technologies/office-2024), [Microsoft Office Excel](https://junglewise.ai/threats/technologies/office-excel), [Microsoft Office Online Server](https://junglewise.ai/threats/technologies/office-online-server). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-100212 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100212 being exploited in the wild.

**How severe is CVE-2026-100212?** High severity, with a CVSS score of 8.8, published 13 October 2026.

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

**Is there a fix for CVE-2026-100212?** 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-2026-100212 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-100212?** Check whether you run Microsoft 365 Apps, Microsoft 365, Microsoft Office 2021 or one of the others listed. 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 use-after-free vulnerability exists in Excel's memory handling logic, allowing an attacker to execute code by sending a malicious file over the network. The vulnerability requires a user to open a specially crafted Excel document; no authentication or elevated privileges are required. Successful exploitation results in remote code execution under the context of the user running Excel.

## Affected products

- Microsoft Office Excel

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-100212](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-100212)

## Related threats

- [Microsoft Office Excel unsafe deserialization in file parsing](https://junglewise.ai/threats/cve-2026-124229-deserialization-of-untrusted-data-in-microsoft-office-excel)
- [Microsoft Office Excel use-after-free remote code execution](https://junglewise.ai/threats/cve-2026-124187-use-after-free-in-microsoft-office-excel-allows-an-unauthorized)
- [Microsoft Office Excel buffer over-read information disclosure](https://junglewise.ai/threats/cve-2026-124183-buffer-over-read-in-microsoft-office-excel-allows-an)
- [Microsoft Office Excel out-of-bounds read information disclosure](https://junglewise.ai/threats/cve-2026-124179-out-of-bounds-read-in-microsoft-office-excel-allows-an)
- [Microsoft Office Excel out-of-bounds read](https://junglewise.ai/threats/cve-2026-124178-out-of-bounds-read-in-microsoft-office-excel-allows-an)