CVE-2026-50467: Microsoft 365 Apps Use-After-Free Flaw

CVE-2026-50467 Overview

CVE-2026-50467 is a use-after-free vulnerability [CWE-416] in Microsoft Office that enables an unauthorized attacker to execute code locally. The flaw affects Microsoft 365 Apps, Microsoft 365 on macOS, and Microsoft Office 2016, 2019, 2021, and 2024 across x86, x64, and macOS builds. Exploitation requires user interaction, typically opening a crafted Office document. Successful attacks compromise the confidentiality, integrity, and availability of the target system.

Critical Impact
An attacker who successfully exploits CVE-2026-50467 can execute arbitrary code in the context of the logged-on user, enabling local code execution across every supported Microsoft Office release.

Affected Products

Microsoft 365 Apps (Enterprise, x86 and x64)
Microsoft 365 for macOS
Microsoft Office 2016, 2019, 2021, and 2024 (including LTSC and macOS builds)

Discovery Timeline

2026-07-14 - CVE-2026-50467 published to NVD
2026-07-16 - Last updated in NVD database

Technical Details for CVE-2026-50467

Vulnerability Analysis

CVE-2026-50467 is a use-after-free condition in Microsoft Office. The application references heap memory after that memory has been freed, allowing an attacker to control the reused allocation and hijack execution flow. Because Office parses complex file formats such as .docx, .xlsx, .pptx, and legacy OLE compound documents, malformed structures can trigger the dangling pointer condition during rendering or object handling.

Exploitation grants code execution in the security context of the user opening the file. On workstations where users hold administrative privileges, this results in full system compromise. The vulnerability applies to both Windows and macOS builds of Office, indicating the affected component is part of the shared cross-platform codebase.

Root Cause

The root cause is improper management of object lifetimes within an Office parsing or rendering component. A pointer continues to reference memory after the underlying object has been released. When the freed region is reallocated with attacker-controlled data, subsequent dereferences read or write into a memory layout the attacker controls, enabling arbitrary code execution.

Attack Vector

The attack vector is local and requires user interaction. An attacker delivers a crafted Office document via email attachment, phishing link, network share, or web download. Opening the document in a vulnerable version of Office triggers the use-after-free and executes the attacker's payload. No prior authentication to the target system is required beyond the interactive user session.

Refer to the Microsoft Security Update CVE-2026-50467 advisory for component-level technical details.

Detection Methods for CVE-2026-50467

Indicators of Compromise

Office processes (winword.exe, excel.exe, powerpoint.exe) spawning script interpreters such as cmd.exe, powershell.exe, or wscript.exe.
Unexpected crashes of Office applications with exception codes consistent with heap corruption or access violations on freed memory.
Office documents originating from untrusted sources containing embedded objects, ActiveX controls, or unusually large or malformed OLE streams.
Outbound network connections initiated by Office processes to previously unseen domains or IP addresses shortly after document open.

Detection Strategies

Monitor parent-child process relationships where Office applications create shell or scripting host children, a common post-exploitation pattern.
Alert on Office processes writing executables, DLLs, or scheduled task artifacts to disk under user profile directories.
Enable Microsoft Defender Attack Surface Reduction (ASR) rules that block Office child process creation and Win32 API calls from macros.
Inspect email gateways for Office attachments that carry embedded objects or exploit-like structures targeting known parser components.

Monitoring Recommendations

Aggregate endpoint telemetry from Office processes into a centralized data lake for correlation across the fleet.
Track patch compliance for all Office channels (Current, Monthly Enterprise, Semi-Annual, LTSC) and flag hosts running unpatched builds.
Review crash dumps from WerFault.exe involving Office binaries for signs of exploitation attempts.

How to Mitigate CVE-2026-50467

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50467 to all affected Office installations.
Prioritize patching for users who routinely open externally sourced documents, including finance, HR, and executive assistants.
Enable Protected View and Office Application Guard where supported to isolate documents from untrusted locations.
Enforce Attack Surface Reduction rules that block Office applications from creating child processes and injecting into other processes.

Patch Information

Microsoft has released security updates addressing CVE-2026-50467 for Microsoft 365 Apps, Microsoft 365 for macOS, Office 2016, Office 2019, Office 2021, and Office 2024. Deploy the updates through Microsoft Update, Click-to-Run, WSUS, Microsoft Intune, or the Microsoft AutoUpdate client on macOS. Consult the Microsoft Security Update Guide entry for CVE-2026-50467 for exact build numbers per channel.

Workarounds

Block or quarantine Office documents from external senders at the mail gateway until patches are applied.
Disable macros and ActiveX controls in Office via Group Policy for users who do not require them.
Configure the File Block policy to prevent opening of legacy or high-risk Office formats from untrusted zones.
Train users to open unexpected Office attachments only in Protected View and never enable editing on unverified files.

bash

# Example Group Policy registry settings to enforce Protected View and disable macros
# Apply via Group Policy Preferences or Intune configuration profiles

reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableInternetFilesInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableAttachmentsInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Word\Security" /v VBAWarnings /t REG_DWORD /d 4 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Excel\Security" /v VBAWarnings /t REG_DWORD /d 4 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\PowerPoint\Security" /v VBAWarnings /t REG_DWORD /d 4 /f