EUVD-2026-44213
GHSA-mpf7-wp9r-5pwf
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
File-open vector so AV:L and UI:R; no auth needed (PR:N); low complexity for a crafted document; code runs in user context yielding full C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
AnalysisAI
Local code execution in Microsoft Office (2016, 2019, LTSC 2021/2024, 365 Apps for Enterprise, and Office for Mac) arises from a heap-based buffer overflow (CWE-122) that an attacker triggers by getting a victim to open a maliciously crafted Office document. Rated CVSS 7.8 with high impact to confidentiality, integrity, and availability, exploitation requires user interaction but no prior authentication or privileges. There is no public exploit identified at time of analysis, and it is not listed in CISA KEV, but Microsoft has released a patch via the MSRC update guide.
Technical ContextAI
The flaw is a CWE-122 heap-based buffer overflow within Microsoft Office's document parsing/rendering code. Heap overflows occur when a program writes more data into a heap-allocated buffer than it was sized for, corrupting adjacent heap metadata or object pointers; a carefully shaped input file can groom the heap so that this corruption is turned into control of execution flow. The CPE data confirms the affected surface is the Office application family across Windows and macOS - Microsoft 365 Apps for Enterprise, Office 2016, Office 2019, Office LTSC 2021, Office LTSC 2024, and their macOS counterparts (Office 365 for Mac, Office LTSC for Mac 2021 and 2024) - meaning the vulnerable component is shared parsing logic common to these builds rather than a single edition. The Microsoft-authored advisory attributes the fix to the vendor's own reporting.
RemediationAI
Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-55140 documented at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55140, selecting the fixed build for your specific channel (Current, Monthly Enterprise, or Semi-Annual for 365 Apps; the LTSC servicing updates for 2016/2019/2021/2024; and the corresponding macOS updates). Because the provided data does not enumerate exact patched build numbers, confirm the target build from the MSRC page rather than relying on assumed version strings. As compensating controls until patching completes, open untrusted documents in Protected View / Application Guard to sandbox rendering, block or quarantine Office file types (and their macro-enabled and legacy binary formats) at the mail gateway, and use Attack Surface Reduction rules and Mark-of-the-Web enforcement so files from the internet are opened read-only - the trade-off is that aggressive blocking of legacy formats and Protected View can disrupt legitimate document workflows and macro-dependent business processes.
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 (Microsoft 365 Apps, Office 2019/LTSC 2021/2024, Word 2016, and the macOS
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
Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Heap Overflow
View allShare
External POC / Exploit Code
Leaving vuln.today