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Microsoft Office Word EUVDEUVD-2026-56423

| CVE-2026-63521 MEDIUM
Out-of-bounds Read (CWE-125)
2026-08-11 secure@microsoft.com GHSA-xc57-cq3p-j9vp
5.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
ENISA EUVD
HIGH
qualitative
vuln.today AI
5.5 MEDIUM

File-based local trigger with mandatory user interaction; no system privileges needed; impact confined to confidentiality with no write or availability consequence.

3.1 AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
4.0 AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

3
Analysis Generated
Aug 11, 2026 - 22:26 vuln.today
Patch available
Aug 11, 2026 - 18:19 EUVD
CVE Published
Aug 11, 2026 - 17:18 nvd
MEDIUM 5.5

DescriptionNVD

Out-of-bounds read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.

AnalysisAI

Out-of-bounds read in Microsoft Office Word exposes high-confidentiality memory contents when a user opens a specially crafted document locally. Affected products span Word 2016, Office 2019, Office LTSC 2021/2024, and Microsoft 365 Apps for Enterprise, confirmed via EUVD-2026-56423. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Craft malicious Word document
Delivery
Deliver file via phishing or shared storage
Exploit
Victim opens document in Word
Execution
Out-of-bounds read triggered in document parser
Impact
In-process Word memory contents disclosed to attacker-controlled location

Vulnerability AssessmentAI

Exploitation Exploitation unconditionally requires the victim to actively open a specially crafted Word document (UI:R) - passive exposure such as file preview or indexing is not implied by available data. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.5 Medium score (5.5) with vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N correctly captures the constrained exploitability: the local attack vector means an attacker cannot reach this over a network without first delivering the malicious file, and user interaction (UI:R) adds a mandatory social engineering step. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker crafts a malicious Word document containing specifically structured data designed to trigger an out-of-bounds read during Word's document parsing phase. The file is delivered to a target user via phishing email or a shared file location, and when the victim opens it, Word reads beyond the intended buffer boundary, disclosing in-process memory contents. …
Remediation Apply vendor-released patches immediately. … Detailed patch versions, workarounds, and compensating controls in full report.

Threat intelligence, references, and detailed analysis are available after sign-in.

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EUVD-2026-56423 vulnerability details – vuln.today

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