EUVD-2026-56693
GHSA-9mcm-3jwv-v4xr
Severity by source
Sources disagree (Medium–Critical)AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Local file-open trigger sets AV:L and UI:R; no privileges needed; only memory disclosure occurs, so C:H with I:N and A:N.
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
Lifecycle Timeline
3DescriptionCVE.org
Out-of-bounds read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.
AnalysisAI
Out-of-bounds read (CWE-125) in Microsoft Office Word exposes memory contents to a local, unauthenticated attacker who can trick a user into opening a crafted document, resulting in high-confidence information disclosure with no integrity or availability impact. The vulnerability spans eight distinct Office product lines across Windows and Mac, including Office 2016 through LTSC 2024 and Microsoft 365 Apps for Enterprise, broadening the exposure surface considerably. No public exploit code or active exploitation has been identified per SSVC (Exploitation: none); Microsoft has released patches via the standard Office update channel.
Technical ContextAI
CWE-125 (Out-of-Bounds Read) describes a condition where software reads data past the end of an intended buffer, potentially exposing adjacent memory to the caller. In Microsoft Office Word's document parsing logic, a specially crafted input file can trigger this condition, causing the parser to read beyond its allocated buffer and surface potentially sensitive in-process memory contents. The 'Buffer Overflow' tag in the source data is consistent with a memory safety class defect in native parsing code, likely within Word's binary or OOXML format handlers. Affected CPE strings span Microsoft Office 2019, LTSC 2021, LTSC 2024, Word 2016 standalone, Office 365 for Mac, and Microsoft 365 Apps for Enterprise - indicating the vulnerable parsing component is shared across these product lines. The local attack vector (AV:L) means exploitation is bound to the victim's own session rather than a network-reachable service.
RemediationAI
The primary fix is to apply the vendor-released patch via standard Microsoft Office update channels. For Windows-based Office editions (Office 2019, LTSC 2021, LTSC 2024, and Microsoft 365 Apps for Enterprise), apply the update referenced at https://aka.ms/OfficeSecurityReleases. For Word 2016 standalone on Windows, upgrade to version 16.0.5565.1000 or later. For Mac editions (Office 365 for Mac, LTSC for Mac 2021, and LTSC for Mac 2024), upgrade to version 16.112.26081010 or later. Where immediate patching is operationally infeasible, a compensating control is to configure Protected View to open all documents from external sources in read-only sandboxed mode, which reduces - but does not eliminate - the attack surface, since the parsing still occurs. Disabling macros and external content does not directly mitigate an out-of-bounds read in the parser. The MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63528 should be monitored for any updated guidance.
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Same weakness CWE-125 – Out-of-bounds Read
View allSame technique Buffer Overflow
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External POC / Exploit Code
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