EUVD-2026-56445
GHSA-6cm4-q5j4-r599
Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Network delivery via malicious file requires user to open it (UI:R); no attacker privileges needed; full RCE yields complete C/I/A compromise of the Excel process.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionCVE.org
Access of resource using incompatible type ('type confusion') in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
AnalysisAI
Type confusion in Microsoft Office Excel's file-processing engine enables remote code execution when a user opens a specially crafted spreadsheet document. The vulnerability carries a CVSS 8.8 High score with full confidentiality, integrity, and availability impact against the Excel process, requiring only user interaction to trigger - the classic phishing-attachment threat model. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the victim open or interact with a specially crafted Excel file - the CVSS UI:R metric confirms user interaction is mandatory. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 8.8 High vector (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) reflects a low-complexity, network-delivered attack requiring only that a user open a malicious file - consistent with high-volume phishing and malicious-attachment campaigns targeting enterprise users. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker sends a spear-phishing email to an enterprise target with a crafted Excel spreadsheet as an attachment. When the victim opens the file, Excel's document parser triggers a type confusion error during processing of malformed data structures, corrupting memory in a controlled fashion. … |
| Remediation | Apply the Microsoft security update for CVE-2026-65807 via Windows Update or the Microsoft Update Catalog; the exact patched build version must be obtained from the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65807, as a specific fix version was not confirmed in the available input data. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: distribute urgent security bulletin to all employees warning against opening unexpected Excel files, especially from external senders; enable email sandbox/detonation for Excel attachments (.xls, .xlsx, .xlsm) at the gateway level if your email filtering platform supports it. …
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External POC / Exploit Code
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