CVE-2026-45459: Microsoft Office Excel protection mechanism failure security bypass

CVE-2026-45459 · Severity: low · CVSS 3.3 · Published 2026-06-09

A security bypass vulnerability exists in Microsoft Excel, the widely used spreadsheet application. An attacker could exploit this flaw to circumvent built-in security protections, potentially gaining unauthorized access to limited information on a user's local system. Successful exploitation requires a user to interact with a specially crafted file, which could lead to a minor breach of data confidentiality.

Technologies: Microsoft Excel. Vendors: Microsoft.

Quick answers

Is CVE-2026-45459 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-45459 being exploited in the wild.
How severe is CVE-2026-45459?
Low severity, with a CVSS score of 3.3, published 9 June 2026.
Which products and versions are affected?
Microsoft Excel.
Is there a fix for CVE-2026-45459?
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-2026-45459 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-45459?
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 protection mechanism failure (CWE-693) exists in Microsoft Office Excel. The vulnerability allows an unauthorized attacker to bypass local security features, though the impact is limited to a low-level breach of confidentiality (C:L). The attack vector is local and requires user interaction, typically involving a victim opening a malicious file. According to the CVSS vector, the exploit does not require elevated privileges and has no impact on system integrity or availability. Microsoft has released information regarding this vulnerability in their June 2026 update cycle.

Affected products

  • Microsoft Excel

Timeline

  • 2026-06-09: disclosed
  • 2026-06-09: advisory: Microsoft MSRC advisory published

References

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