EUVD-2026-56751
GHSA-jjhm-qqfx-22xc
Severity by source
Sources disagree (Medium–Critical)AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Local file-open trigger with no privileges needed, user must interact; confidentiality-only impact matches heap read disclosure with no write or crash path.
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 VectorNVD
Lifecycle Timeline
3DescriptionNVD
Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to disclose information locally.
AnalysisAI
Heap-based buffer overflow in Microsoft Office Word enables a local, unauthenticated attacker to disclose sensitive memory contents by enticing a user to open a maliciously crafted document. Affected products span Microsoft Word 2016, Microsoft 365 Apps for Enterprise, Office LTSC 2021/2024 on Windows, and Office LTSC/365 on macOS. No public exploit code has been identified at time of analysis, SSVC rates exploitation as none, and Microsoft has released patches via the standard Office update channel.
Technical ContextAI
CWE-122 (Heap-based Buffer Overflow) identifies the root cause: a memory region on the heap is written beyond its allocated boundary during document parsing in Word's processing engine. Heap overflows in document parsers typically arise when attacker-controlled length fields govern copy operations without adequate bounds checking, causing adjacent heap memory - which may contain pointers, tokens, or cached file data - to be exposed. Affected CPE targets include Microsoft Office 2019 (19.0.0), Office LTSC 2021 and 2024 (16.0.x), Microsoft Word 2016 (below 16.0.5565.1000), Microsoft 365 Apps for Enterprise (16.0.x), and macOS variants Office LTSC for Mac 2021, LTSC for Mac 2024, and Office 365 for Mac (all below 16.112.26081010). The vulnerability is limited in scope to confidentiality - no integrity or availability impact is present in the CVSS vector.
RemediationAI
The primary fix is to apply Microsoft's released patch through the standard Office update mechanism. For Windows targets, update to Microsoft Word 2016 version 16.0.5565.1000 or later; all other Windows Office versions (2019, LTSC 2021, LTSC 2024, Microsoft 365 Apps for Enterprise) should be updated via https://aka.ms/OfficeSecurityReleases. For macOS targets, update to version 16.112.26081010 or later across Office LTSC for Mac 2021, LTSC for Mac 2024, and Office 365 for Mac. During the patch window, compensating controls include enabling Protected View for documents received from the internet or email (already default in most enterprise configurations), blocking execution of macros from untrusted sources, and deploying email gateway filtering to quarantine .docx and .rtf attachments from unknown senders. Protected View specifically limits the attack surface by preventing full parsing of untrusted documents. These controls carry minimal operational trade-off for most environments. See the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66810.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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