Summary
Impact: Information Disclosure. Microsoft rating: Important. Not known to be exploited — Exploitation Unlikely. Customer action: Required.
Details
What type of information could be disclosed by this vulnerability?
An attacker who successfully exploited this vulnerability could potentially read portions of process memory.
Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.
Security updates
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.0.5565.1000 — https://support.microsoft.com/help/5002901
Vulnerabilities 1
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Medium 5.5
Microsoft Office Word Information Disclosure Vulnerability
Out-of-bounds read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.
Revision history
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#2
Updated an acknowledgement. This is an informational change only.
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#1
Information published.
References
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CVE-2026-63521 Microsoft Office Word Information Disclosure Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63521
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss