EUVD-2026-56426
GHSA-5j3f-qh27-vxj9
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Local execution triggered by opening a crafted document (AV:L, UI:R); no system privileges required (PR:N); full code execution yields high C/I/A; scope unchanged.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Use after free in Microsoft Office allows an unauthorized attacker to execute code locally.
AnalysisAI
Use-after-free memory corruption in Microsoft Office enables an attacker to execute arbitrary code in the context of the victim user, scoring CVSS 7.8 (High). Affected products span Office 2019, LTSC 2021, LTSC 2024, and Microsoft 365 Apps for Enterprise on both Windows and macOS. Exploitation requires a victim to open a specially crafted Office document - a delivery mechanism trivially achieved via phishing - and no public exploit code or CISA KEV listing has been identified at time of analysis, though Microsoft Office's ubiquitous enterprise footprint and adversary interest in document-borne malware elevate this beyond a theoretical risk.
Technical ContextAI
CWE-416 (Use After Free) describes a class of memory-safety flaw where a program retains a reference to heap memory after that memory has been freed. In Microsoft Office's document processing pipeline, a maliciously crafted file can trigger a sequence in which an in-memory object is deallocated while a dangling pointer to it persists; subsequent dereference of that pointer via controlled document content allows an attacker to achieve write primitives or redirect execution flow. This vulnerability class is well-understood in the Office ecosystem and has historically been the mechanism behind high-profile document-borne malware campaigns. Affected products include Office for Windows (Office 2019, LTSC 2021, LTSC 2024, Microsoft 365 Apps for Enterprise) and Office for Mac (LTSC 2021, LTSC 2024, Office 365 for Mac), as confirmed by ENISA EUVD-2026-56426 and the MSRC advisory.
RemediationAI
Apply the vendor-released patch immediately. For macOS installations, upgrade to build 16.112.26081010 or later (confirmed patched version per EUVD-2026-56426). For Windows installations across Office 2019, LTSC 2021, LTSC 2024, and Microsoft 365 Apps for Enterprise, the specific patched build must be obtained from https://aka.ms/OfficeSecurityReleases - exact Windows build numbers were not independently confirmed in the available data and should be verified there before declaring remediation complete. Where immediate patching is not feasible, enable Protected View in Office (File > Trust Center > Protected View > enable all three Protected View options) to sandbox externally-sourced and email-attached documents in a read-only mode that blocks automatic code execution; note this will require users to actively click 'Enable Editing' for legitimate files and may affect workflow. Additionally, deploying endpoint security solutions with AMSI integration can detect malicious Office documents at load time. Do not rely on blocking macros alone, as use-after-free exploitation does not necessarily require VBA macro execution.
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Same weakness CWE-416 – Use After Free
View allSame technique Denial Of Service
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External POC / Exploit Code
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