CVE-2026-78515 Advisory
Severity: MEDIUM (CVSS 6.5)
Affected Product:
- Microsoft Defender Business
Vulnerability: Out-of-bounds read in Microsoft Office Excel allows unauthorized disclosure of information over a network.
KEV Status: Not currently exploited in active campaigns
Remediation: Apply security updates from Microsoft. Refer to the official advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78515
Recommended Action: Prioritize patching based on your organization’s Excel usage and network exposure. Standard change management procedures apply.