Quick answers
- Is CVE-2026-100209 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-100209 being exploited in the wild.
- How severe is CVE-2026-100209?
- 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-2026-100209?
- 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-2026-100209 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-100209?
- 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, allowing an attacker to execute code by crafting a malicious spreadsheet file. The vulnerability requires user interaction (opening a file) and can be delivered over a network. Exploitation grants the attacker arbitrary code execution in the context of the user running Excel.
Affected products
- Microsoft Office Excel
Timeline
- 2026-10-13: disclosed