CVE-2025-30377: Microsoft 365 Apps Use After Free Flaw

CVE-2025-30377 Overview

CVE-2025-30377 is a use-after-free vulnerability in Microsoft Office that allows an unauthorized attacker to execute arbitrary code locally on the affected system. This memory corruption flaw occurs when the application references memory after it has been freed, potentially allowing attackers to manipulate program execution flow and achieve code execution with the privileges of the current user.

Critical Impact

Successful exploitation of this use-after-free vulnerability enables local code execution, potentially allowing attackers to gain complete control over the affected system with the privileges of the logged-in user.

Affected Products

• Microsoft 365 Apps (Enterprise)
• Microsoft Excel 2016
• Microsoft Office 2019
• Microsoft Office Long Term Servicing Channel 2021 (Windows and macOS)
• Microsoft Office Long Term Servicing Channel 2024 (Windows and macOS)
• Microsoft Office Online Server

Discovery Timeline

• 2025-05-13 - CVE-2025-30377 published to NVD
• 2025-05-19 - Last updated in NVD database

Technical Details for CVE-2025-30377

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption vulnerability class that occurs when a program continues to use a pointer after the memory it references has been deallocated. In the context of Microsoft Office, this creates an exploitable condition where an attacker can potentially control the contents of the freed memory region.

Use-after-free vulnerabilities are particularly dangerous in complex applications like Microsoft Office because they can be leveraged to achieve arbitrary code execution. When memory is freed but a dangling pointer remains, subsequent allocation operations may reuse that memory space. If an attacker can influence the contents of this reallocated memory, they can manipulate program execution when the application later dereferences the stale pointer.

The local attack vector indicates that exploitation requires the attacker to have local access to the system or to convince a user to open a maliciously crafted document. Given the nature of Office applications, the most likely attack scenario involves a specially crafted Office document that triggers the use-after-free condition during parsing or rendering operations.

Root Cause

The root cause is improper memory management within Microsoft Office components where memory is freed but references to that memory are not properly invalidated. This creates a temporal window where the application maintains pointers to deallocated memory regions, leading to undefined behavior when those pointers are subsequently accessed.

Attack Vector

The attack vector is local, meaning successful exploitation requires either direct local access to the target system or user interaction with a malicious file. The most probable exploitation scenario involves:

1. An attacker crafting a malicious Office document (such as .docx, .xlsx, or similar formats) that triggers the vulnerable code path
2. A user opening the malicious document in an affected version of Microsoft Office
3. The document triggering the use-after-free condition during parsing or rendering
4. The attacker achieving code execution in the context of the user running the Office application

The vulnerability exploitation mechanism relies on careful manipulation of memory allocation patterns to place attacker-controlled data in the freed memory region before the dangling pointer is dereferenced. See the Microsoft Security Advisory for complete technical details.

Detection Methods for CVE-2025-30377

Indicators of Compromise

• Unexpected crashes or abnormal termination of Microsoft Office applications
• Office processes spawning unexpected child processes or exhibiting unusual behavior
• Memory access violations or application errors logged in Windows Event Logs
• Suspicious Office documents from untrusted sources with unusual structure or embedded content

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions capable of monitoring Office application behavior for signs of memory corruption exploitation
• Implement application whitelisting to prevent unauthorized code execution from Office processes
• Monitor for anomalous process creation chains originating from Office applications (e.g., WINWORD.EXE spawning cmd.exe or powershell.exe)
• Enable crash dump analysis to identify exploitation attempts targeting this vulnerability

Monitoring Recommendations

• Configure SentinelOne to monitor Microsoft Office processes for behavioral anomalies indicative of exploitation
• Enable enhanced logging for Office application events and Windows Error Reporting
• Implement network monitoring to detect command-and-control communications from potentially compromised Office processes
• Review Office file downloads and email attachments for suspicious characteristics

How to Mitigate CVE-2025-30377

Immediate Actions Required

• Apply the latest Microsoft security updates for all affected Office products immediately
• Ensure Microsoft 365 Apps are configured for automatic updates to receive patches promptly
• Restrict the opening of Office documents from untrusted sources
• Consider implementing Protected View settings to open documents in a sandboxed environment

Patch Information

Microsoft has released security updates to address this vulnerability. Administrators should consult the Microsoft Security Response Center advisory for CVE-2025-30377 for specific patch versions and deployment guidance. Organizations using Microsoft 365 Apps for Enterprise should ensure their update channel is configured to receive the latest security updates.

Workarounds

• Enable Protected View for all Office documents originating from the internet or untrusted locations
• Configure Microsoft Office to block macros and active content in documents from external sources
• Utilize Application Guard for Office when available to isolate potentially malicious documents
• Train users to be cautious when opening Office documents from unknown or suspicious sources

# PowerShell: Enable Protected View for Internet files in Office
# Run as Administrator

# Set Protected View for files originating from the Internet
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableInternetFilesInPV" -Value 0 -Type DWord
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" -Name "DisableInternetFilesInPV" -Value 0 -Type DWord

# Enable Protected View for Outlook attachments
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableAttachmentsInPV" -Value 0 -Type DWord
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" -Name "DisableAttachmentsInPV" -Value 0 -Type DWord