EUVD-2026-56749
GHSA-v63q-fh49-r4gg
Severity by source
Sources disagree (Low–High)AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Local file-based delivery (AV:L) with mandatory user interaction (UI:R); no system authentication needed (PR:N); full impact triad warranted for arbitrary code execution.
vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionCVE.org
Stack-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
AnalysisAI
Stack-based buffer overflow in Microsoft Office enables local arbitrary code execution when a user opens a specially crafted document. The CVSS vector (AV:L/AC:L/PR:N/UI:R) confirms exploitation is local and requires user interaction - most likely triggered by opening a maliciously crafted Office file delivered via phishing or other social engineering. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the victim to actively open or interact with a specially crafted Microsoft Office document on a system running a vulnerable Office version (UI:R) - the attacker cannot trigger the overflow remotely without this user action. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 7.8 High score reflects full C/I/A impact but is constrained by AV:L and UI:R, which together require both file delivery to the victim system and user-initiated interaction - direct remote unauthenticated exploitation is not possible. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker crafts a malicious Microsoft Office document containing input specifically designed to overflow a stack buffer in a vulnerable Office parsing routine, then delivers it to the victim via a phishing email, malicious download link, or shared drive. When the victim opens the document with an affected version of Microsoft Office, the overflow corrupts the stack and redirects execution to attacker-controlled shellcode or ROP chain, achieving arbitrary code execution under the victim's user account. … |
| Remediation | Apply the vendor-released security update via Microsoft Update, Windows Update for Business, or the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66807. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Office deployments across the organization and assess user-facing risk; communicate vulnerability status to security and IT teams and prepare incident response protocols. …
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Same weakness CWE-121 – Stack-based Buffer Overflow
View allSame technique Stack Overflow
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External POC / Exploit Code
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