EUVD-2026-44163
GHSA-65j6-99mv-3xg6
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Exploitation is via opening a crafted document (AV:L, UI:R) with no prior privileges (PR:N); successful use-after-free yields code execution in user context, giving full C:H/I:H/A:H.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Microsoft Office allows an unauthorized attacker to execute code locally.
AnalysisAI
Local code execution in Microsoft Office (2016, 2019, LTSC 2021/2024, Microsoft 365 Apps for Enterprise, and Office for Mac) stems from a use-after-free memory corruption (CWE-416) that an attacker triggers when a victim opens a maliciously crafted document. Rated CVSS 7.8 with high confidentiality, integrity, and availability impact, exploitation requires user interaction but no prior authentication, letting an attacker run arbitrary code in the context of the current user. There is no public exploit identified at time of analysis and it is not listed in CISA KEV, but Microsoft has released a fix, so patching should be prioritized during the normal Patch Tuesday cycle.
Technical ContextAI
The flaw is a use-after-free (CWE-416), a memory-corruption class in which application code continues to reference an object after its backing memory has been freed, allowing an attacker who controls the freed-then-reallocated memory to hijack execution flow. The CPE data confirms the vulnerable component is the Microsoft Office application suite across Windows builds (Microsoft 365 Apps for Enterprise, Office 2016, Office 2019, Office LTSC 2021, Office LTSC 2024) and macOS builds (Office 365 for Mac, Office LTSC for Mac 2021 and 2024), indicating the defect lives in shared cross-platform Office parsing or object-lifecycle code rather than an OS-specific layer. Such bugs typically reside in the file-format parsers that deserialize complex document structures, where dangling pointers to freed document objects can be reclaimed by attacker-controlled data.
RemediationAI
Apply the Microsoft-provided update for your Office channel; patch is available per vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55018 - the supplied data does not enumerate an exact fixed build, so pull the specific patched version for each SKU (Click-to-Run for Microsoft 365 Apps, MSI/LTSC packages, and the Mac AutoUpdate channel) directly from that MSRC page. Until updates are deployed, reduce exposure by enabling Protected View for files originating from the internet and email (the default, but confirm it is enforced by policy) and by blocking or gating untrusted Office attachments at the mail gateway, accepting the trade-off of added friction when users legitimately need to edit externally sourced documents. Because exploitation requires opening a crafted file, user-awareness guidance to not enable editing on unexpected documents is a meaningful interim control, though not a substitute for patching.
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-416 – Use After Free
View allSame technique Use After Free
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External POC / Exploit Code
Leaving vuln.today