CVE-2025-49702: Microsoft 365 Apps RCE Vulnerability

CVE-2025-49702 Overview

CVE-2025-49702 is a type confusion vulnerability in Microsoft Office that allows an unauthorized attacker to execute code locally on a victim's machine. The flaw is classified under [CWE-843] (Access of Resource Using Incompatible Type) and affects multiple supported Office releases, including Microsoft 365 Apps, Microsoft 365 Copilot, Office 2016, Office 2019, and Office Long Term Servicing Channel 2021 and 2024. Exploitation requires user interaction, typically opening a crafted Office document. Microsoft published the advisory on July 8, 2025.

Critical Impact

Successful exploitation grants the attacker the ability to execute arbitrary code in the context of the user running Office, resulting in full compromise of confidentiality, integrity, and availability on the affected host.

Affected Products

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

Discovery Timeline

• 2025-07-08 - CVE-2025-49702 published to the National Vulnerability Database (NVD)
• 2026-05-22 - Last updated in NVD database

Technical Details for CVE-2025-49702

Vulnerability Analysis

The vulnerability resides in Microsoft Office's parsing logic, where an object of one type is accessed as if it were a different, incompatible type. When Office processes a maliciously crafted document, the type confusion causes the application to treat a memory region as a structure it was not allocated for. This mismatch enables an attacker to manipulate object metadata, function pointers, or virtual table dispatch, ultimately redirecting execution flow to attacker-controlled code.

Because the attack vector is local and user interaction is required, exploitation depends on social engineering. An attacker delivers a weaponized document through email, a file share, or a download link, and the victim opens it in a vulnerable Office client. Code then runs at the privilege level of the logged-in user.

Root Cause

The root cause is improper validation of object type before access, characteristic of [CWE-843] flaws. Office's document parsers do not consistently verify that a referenced object matches the expected type signature before dereferencing fields or invoking methods. This permits an attacker to forge or substitute objects within a document stream to trigger a type mismatch during deserialization or rendering.

Attack Vector

The attacker crafts an Office document, such as a Word, Excel, or PowerPoint file, containing embedded structures that trigger the type confusion when parsed. Delivery occurs through phishing, malicious attachments, or compromised file-sharing services. Once the user opens the document, Office processes the malformed structure and the type confusion executes attacker-supplied code in the user's session, bypassing the need for elevated privileges.

No public proof-of-concept exploit has been published. The EPSS probability stands at 0.792% as of the most recent scoring, indicating limited but non-trivial exploitation likelihood.

Detection Methods for CVE-2025-49702

Indicators of Compromise

• Unexpected child processes spawned by winword.exe, excel.exe, powerpnt.exe, or outlook.exe, such as cmd.exe, powershell.exe, rundll32.exe, or regsvr32.exe
• Office processes writing executable files (.exe, .dll, .scr) or scripts to user-writable paths like %APPDATA%, %TEMP%, or %LOCALAPPDATA%
• Outbound network connections initiated directly by Office binaries to uncommon external hosts
• Office documents arriving from untrusted external senders with macros, embedded objects, or unusual file size anomalies

Detection Strategies

• Monitor process lineage where an Office application is the parent of scripting interpreters or LOLBins
• Inspect document attachments at the email gateway for malformed structures and known exploit signatures
• Correlate Office crashes (Windows Error Reporting events) with subsequent suspicious process activity on the same host

Monitoring Recommendations

• Enable Microsoft Defender Attack Surface Reduction (ASR) rules that block Office applications from creating child processes and executable content
• Forward Sysmon process creation, image load, and network connection events to a SIEM for behavioral correlation
• Audit Office telemetry for repeated parser failures, which often precede successful exploitation attempts

How to Mitigate CVE-2025-49702

Immediate Actions Required

• Apply the Microsoft security update referenced in Microsoft Security Update CVE-2025-49702 to all affected Office installations
• Inventory endpoints to confirm patch deployment across Microsoft 365 Apps, Office 2016, 2019, and LTSC 2021/2024 builds, including macOS clients
• Block or quarantine inbound Office documents from untrusted external senders at the email security gateway
• Restrict execution of Office macros and embedded content by policy until patching completes

Patch Information

Microsoft released a security update addressing CVE-2025-49702 on July 8, 2025. Refer to the Microsoft Security Response Center advisory for the specific build numbers and KB articles applicable to each affected channel and platform. Administrators should validate update installation through Microsoft Update, Microsoft 365 Apps admin center, or their enterprise patch management tool.

Workarounds

• Enable Office Protected View and Application Guard to isolate documents originating from the internet or other untrusted locations
• Configure ASR rules to block Office child process creation and executable content creation
• Open suspicious or unsolicited documents only in a sandboxed environment until patches are applied

# Enable Microsoft Defender ASR rules to reduce Office exploitation risk
# Block Office applications from creating child processes
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A -AttackSurfaceReductionRules_Actions Enabled

# Block Office applications from creating executable content
Set-MpPreference -AttackSurfaceReductionRules_Ids 3B576869-A4EC-4529-8536-B80A7769E899 -AttackSurfaceReductionRules_Actions Enabled

# Block Win32 API calls from Office macros
Set-MpPreference -AttackSurfaceReductionRules_Ids 92E97FA1-2EDF-4476-BDD6-9DD0B4DDDC7B -AttackSurfaceReductionRules_Actions Enabled