CVE-2025-49696: Microsoft 365 Apps RCE Vulnerability

CVE-2025-49696 Overview

CVE-2025-49696 is an out-of-bounds read vulnerability in Microsoft Office that allows an unauthorized attacker to execute arbitrary code locally. This memory corruption flaw affects multiple versions of Microsoft Office products across Windows, macOS, and Android platforms, presenting a significant risk to enterprise environments relying on Microsoft productivity software.

Critical Impact

An out-of-bounds read vulnerability enabling local code execution without requiring user interaction or special privileges could allow attackers to compromise systems and potentially gain full control over affected Microsoft Office installations.

Affected Products

• Microsoft 365 Apps for Enterprise (x64 and x86)
• Microsoft Office 2016, 2019 (x64 and x86)
• Microsoft Office Long Term Servicing Channel 2021 and 2024 (Windows x64/x86 and macOS)
• Microsoft Office for Android

Discovery Timeline

• July 8, 2025 - CVE-2025-49696 published to NVD
• July 15, 2025 - Last updated in NVD database

Technical Details for CVE-2025-49696

Vulnerability Analysis

This vulnerability stems from improper memory handling within Microsoft Office components. The out-of-bounds read condition (CWE-125) occurs when the application reads data beyond the boundaries of an allocated buffer, which can lead to information disclosure or memory corruption. Additionally, the vulnerability is associated with a heap-based buffer overflow (CWE-122), indicating that the out-of-bounds read may occur within heap-allocated memory regions.

The combination of these memory safety issues creates conditions where an attacker can potentially leverage the out-of-bounds read to leak memory contents, bypass security mechanisms such as Address Space Layout Randomization (ASLR), or chain with other vulnerabilities to achieve code execution. The local attack vector requires the attacker to have some form of access to the target system, though no privileges or user interaction are required to exploit the vulnerability.

Root Cause

The root cause of CVE-2025-49696 lies in insufficient bounds checking when processing data within Microsoft Office. The application fails to properly validate buffer boundaries before performing read operations, allowing memory access outside the intended buffer limits. This type of memory safety violation is characteristic of CWE-125 (Out-of-bounds Read) and is compounded by the heap-based buffer overflow condition (CWE-122), which suggests the vulnerable code path involves dynamically allocated memory on the heap.

Attack Vector

The attack vector for this vulnerability is local, meaning an attacker would need to execute malicious code on the target system or deliver a specially crafted document that triggers the vulnerability when processed by Microsoft Office. The exploitation does not require any user interaction or elevated privileges, making it particularly dangerous in scenarios where:

• A malicious document is opened by the victim
• A local attacker runs code to trigger the vulnerable code path
• Automated document processing pipelines handle attacker-controlled content

The vulnerability affects Microsoft Office across multiple platforms including Windows (both 32-bit and 64-bit architectures), macOS, and Android, broadening the potential attack surface significantly.

Detection Methods for CVE-2025-49696

Indicators of Compromise

• Unexpected crashes or error conditions in Microsoft Office applications during document processing
• Memory access violations or exception handling events logged in Windows Event Viewer related to Office processes
• Anomalous process behavior from Office executables such as WINWORD.EXE, EXCEL.EXE, or POWERPNT.EXE
• Suspicious document files with malformed or unusual embedded objects

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions to monitor for exploitation attempts targeting Microsoft Office processes
• Enable memory protection features such as ASLR, DEP, and Control Flow Guard on systems running Microsoft Office
• Implement file integrity monitoring for Office binary files and configuration settings
• Monitor for abnormal parent-child process relationships involving Office applications

Monitoring Recommendations

• Configure security information and event management (SIEM) systems to alert on Office application crashes and memory exceptions
• Enable Windows Defender Exploit Guard to detect and block exploitation techniques
• Review application logs for Microsoft Office crash dumps and analyze for exploitation indicators
• Deploy network monitoring to detect suspicious document transfers that may contain exploit payloads

How to Mitigate CVE-2025-49696

Immediate Actions Required

• Apply the latest Microsoft security updates for all affected Office products immediately
• Review and restrict local access to systems running vulnerable Microsoft Office versions
• Enable Protected View and other sandboxing features in Microsoft Office applications
• Block or quarantine suspicious documents from untrusted sources until patches are applied

Patch Information

Microsoft has released security updates to address CVE-2025-49696. Detailed patch information and download links are available in the Microsoft Security Update Guide. Organizations should prioritize patching across all affected Microsoft Office installations including Microsoft 365 Apps, Office 2016, Office 2019, and Office Long Term Servicing Channel versions (2021 and 2024) on all supported platforms.

Workarounds

• Enable Protected View for files originating from the Internet, email attachments, and potentially unsafe locations
• Configure Microsoft Office to open documents in read-only mode by default for untrusted sources
• Implement application whitelisting to restrict execution of potentially malicious macros and embedded content
• Consider using Microsoft Office Online or other web-based alternatives until patches can be applied

# PowerShell: Enable Protected View settings via registry
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableAttachmentsInPV" -Value 0
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableInternetFilesInPV" -Value 0
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableUnsafeLocationsInPV" -Value 0