EUVD-2026-56752
GHSA-fc76-3hc4-hv86
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Local vector because exploitation requires victim to open a crafted file; PR:N as no attacker system privileges needed; C:H for potential sensitive memory disclosure; no integrity or availability impact.
Primary rating from NVD.
CVSS VectorNVD
Lifecycle Timeline
3DescriptionNVD
Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.
AnalysisAI
Out-of-bounds read in Microsoft Office exposes memory contents to local information disclosure across a wide range of affected products including Word 2016, Office 2019, LTSC 2021/2024, Microsoft 365 Apps for Enterprise, and Office 365/LTSC for Mac. The CVSS vector (AV:L/UI:R/C:H) indicates exploitation requires a victim to open a specially crafted Office document, after which sensitive in-process memory can be disclosed to the attacker. No public exploit has been identified at time of analysis, no KEV listing exists, and Microsoft has released patches across all affected product lines.
Technical ContextAI
CWE-125 (Out-of-bounds Read) describes a condition where a program reads beyond the boundary of an allocated memory buffer, potentially exposing adjacent heap or stack contents. Despite the 'Buffer Overflow' tag in the source data, the CWE classification correctly identifies this as a read-side memory safety flaw, not a write-based overflow - an important distinction because it limits impact to confidentiality rather than enabling code execution. The flaw resides in Microsoft Office's document processing components, affecting both Windows builds (Office 2016-2024 LTSC, Microsoft 365 Apps for Enterprise) and macOS builds (Office 365 for Mac, LTSC for Mac 2021/2024) as confirmed by EUVD CPE data. The specific parser or rendering subsystem is not identified in available data.
RemediationAI
Microsoft has released patches across all affected product lines. For macOS builds (Office 365 for Mac, LTSC for Mac 2021, LTSC for Mac 2024), update to version 16.112.26081010 or later via Microsoft AutoUpdate or the Mac App Store. For Microsoft Word 2016 on Windows, update to 16.0.5565.1000 or later. For Microsoft Office 2019, LTSC 2021, LTSC 2024, and Microsoft 365 Apps for Enterprise on Windows, apply the latest update as detailed at https://aka.ms/OfficeSecurityReleases via Windows Update, Microsoft Update Catalog, or Office Click-to-Run channels. Organizations unable to patch immediately should consider restricting the opening of Office documents from untrusted sources using Protected View policies (already enabled by default for files from the internet in modern Office versions) - note that Protected View does not fully isolate the parsing path in all builds, so patching remains the definitive fix. The MSRC advisory is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66809.
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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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