EUVD-2026-56422
GHSA-mvf6-42fg-9rcw
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
AV:L reflects file-based triggering requiring local document open; UI:R because victim must open the crafted file; PR:N as the attacker needs no prior system access; full C/I/A impact consistent with arbitrary code execution.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code locally.
AnalysisAI
Heap-based buffer overflow in Microsoft Office Word enables arbitrary local code execution when a user opens a specially crafted document. The vulnerability spans a broad set of affected products across both Windows and macOS platforms, including Office LTSC 2021/2024, Office 2019, Microsoft 365 Apps for Enterprise, Office 365 for Mac, and Outlook 2016. No public exploit code has been identified at time of analysis, though Microsoft has released a patch and the document-based delivery model is a proven and widely abused attack vector in enterprise phishing campaigns.
Technical ContextAI
CWE-122 (Heap-based Buffer Overflow) describes a condition where a write operation exceeds the bounds of a heap-allocated buffer, corrupting adjacent memory - which can include heap metadata, vtable pointers, or adjacent object data - and redirect program execution to attacker-controlled code. The vulnerability resides in Microsoft Word's document parsing engine. The presence of both Windows and macOS product families in the affected version list (including Office LTSC for Mac and Office 365 for Mac) indicates the vulnerable code is present in a shared or cross-platform component of Word's file-handling logic. Outlook 2016's inclusion suggests it is affected through its integration with Word for document composition or preview rendering. The CVSS vector AV:L/UI:R is consistent with a crafted-file attack: the overflow is triggered during parsing of a malicious document when a local user opens it.
RemediationAI
Apply Microsoft's patch immediately via the standard Office update channel. For Windows-based products - Office LTSC 2021, LTSC 2024, Office 2019, and Microsoft 365 Apps for Enterprise - updates are available through https://aka.ms/OfficeSecurityReleases. For macOS-based products - Office 365 for Mac, LTSC for Mac 2021, and LTSC for Mac 2024 - update to version 16.112.26081010 or later. For Microsoft Outlook 2016, update to version 16.0.5565.1000 or later. Where immediate patching is not feasible, ensure Office Protected View is configured to open documents received from the internet or email attachments in read-only mode, reducing but not eliminating the attack surface; note that Protected View can be bypassed by social engineering that induces users to enable editing. Enabling Microsoft's Attack Surface Reduction rule 'Block Office applications from creating child processes' (GUID: d4f940ab-401b-4efc-aadc-ad5f3c50688a) can limit post-exploitation impact by preventing the spawned process from launching secondary payloads, though this may affect legitimate Office automation workflows.
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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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