EUVD-2026-44209
GHSA-29qv-mf54-6cq7
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Local crafted-file vector with mandatory user interaction (AV:L/UI:R), no attacker auth (PR:N), and full RCE-level impact in the user context (C/I/A:H).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code locally.
AnalysisAI
Local code execution in Microsoft Office Word (Microsoft 365 Apps, Office 2019/LTSC 2021/2024, Word 2016, and the macOS builds) arises from a stack-based buffer overflow triggered when a victim opens a maliciously crafted document. The CVSS 3.1 vector (AV:L/AC:L/PR:N/UI:R) shows an unauthenticated attacker needs no privileges but does require user interaction, and successful exploitation yields full confidentiality, integrity, and availability impact in the user's security context. There is no public exploit identified at time of analysis and it is not listed in CISA KEV, but Microsoft has released a patch.
Technical ContextAI
The flaw is a CWE-121 stack-based buffer overflow in Word's file-parsing code path. When Word processes a specially crafted document, it copies attacker-controlled data into a fixed-size stack buffer without adequate bounds checking, allowing corruption of the return address and adjacent stack variables to hijack control flow. Per the CPE data the vulnerable parsing component ships across the Office/Word family - Microsoft 365 Apps for Enterprise, Office 2019, Office LTSC 2021 and 2024, Word 2016, and the Office for Mac / Office LTSC for Mac 2021 and 2024 builds - and the same document-handling code is also surfaced through SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition, which parse Office documents server-side. Because the overflow lives in shared Office rendering/parsing logic rather than a single binary, the affected surface spans both desktop clients and server products.
RemediationAI
Apply the Microsoft security update for CVE-2026-55134 as the primary fix - Patch available per vendor advisory - using the guidance and per-product build numbers published at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55134 (exact fixed versions were not provided in the input data and should be taken directly from MSRC). Ensure Click-to-Run channels for Microsoft 365 Apps and the LTSC/perpetual and macOS builds are all updated, and patch the SharePoint servers as well. Until patched, reduce exposure by opening untrusted documents in Protected View / Application Guard and keeping macros disabled (side effect: users must explicitly trust files to edit them), blocking or quarantining Word documents from external email and web sources at the mail/proxy gateway (side effect: may delay legitimate documents), and restricting SharePoint document-processing endpoints to trusted users (side effect: reduced collaboration reach). These are compensating controls only and do not remove the underlying overflow.
Local code execution in Microsoft Word (and Office/SharePoint components that render Word content) stems from an integer
Arbitrary code execution in Microsoft Office Word (and the broader Office/365/SharePoint family) arises from a stack-bas
Local code execution in Microsoft Word (part of Microsoft 365 Apps, Office 2019, Office LTSC 2021/2024, and Office for M
Arbitrary code execution in Microsoft PowerPoint (and the broader Microsoft Office/365 suite on Windows and macOS) arise
Local code execution in Microsoft Office PowerPoint (including Microsoft 365 Apps, Office 2019, Office LTSC 2021/2024, a
Local code execution in Microsoft Office PowerPoint (CWE-122 heap-based buffer overflow) lets an unauthorized attacker r
Local code execution in Microsoft Word (and the wider Microsoft Office / Microsoft 365 Apps family) lets an unauthorized
Local code execution in Microsoft Word (Office 2016/2019, Microsoft 365 Apps, Office LTSC 2021/2024) arises from a heap-
Local code execution in Microsoft Office Word (CWE-416 use-after-free) allows an unauthorized attacker to run arbitrary
Local code execution in Microsoft Office Word (via a stack-based buffer overflow, CWE-121) lets an attacker run arbitrar
Local code execution in Microsoft Office Word (across Microsoft 365 Apps, Office 2019/LTSC 2021/2024, Office for Mac, an
Numeric truncation error (CWE-197) in Microsoft Office Word triggers local information disclosure when a user opens a ma
Same weakness CWE-121 – Stack-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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