Quick answers
- Is CVE-2026-40359 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-40359 being exploited in the wild.
- How severe is CVE-2026-40359?
- High severity, with a CVSS score of 7.8, published 12 May 2026.
- Which products and versions are affected?
- Microsoft Excel.
- Is there a fix for CVE-2026-40359?
- 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-2026-40359 attacked?
- It is attacked with local access, in a network appliance.
- Am I affected by CVE-2026-40359?
- 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
A use-after-free vulnerability (CWE-416) exists in Microsoft Office Excel. The flaw is triggered when the application attempts to use memory that has already been deallocated, leading to memory corruption. An attacker can exploit this by convincing a user to open a maliciously crafted Excel document. Successful exploitation requires user interaction but no prior administrative privileges, allowing the attacker to execute arbitrary code with the same permissions as the logged-in user. Microsoft has released information regarding this vulnerability in their security update guide.
Affected products
- Microsoft Excel
Timeline
- 2026-05-12: disclosed
- 2026-05-12: advisory