CVE-2025-47994: Microsoft 365 Apps Privilege Escalation

CVE-2025-47994 Overview

CVE-2025-47994 is a high-severity insecure deserialization vulnerability affecting Microsoft Office products that allows an unauthorized attacker to elevate privileges locally. The vulnerability exists due to improper handling of untrusted data during deserialization operations within Microsoft Office components, potentially enabling attackers to execute arbitrary code with elevated privileges on the target system.

Critical Impact

This vulnerability allows local privilege escalation through deserialization of untrusted data, potentially enabling attackers to gain elevated system access and compromise affected Microsoft Office installations across enterprise environments.

Affected Products

• Microsoft 365 Apps (Enterprise, x64 and x86)
• Microsoft Office 2016, 2019 (x64 and x86)
• Microsoft Office LTSC 2021 and 2024 (x64 and x86)
• Microsoft SharePoint Enterprise Server 2016

Discovery Timeline

• July 8, 2025 - CVE-2025-47994 published to NVD
• July 15, 2025 - Last updated in NVD database

Technical Details for CVE-2025-47994

Vulnerability Analysis

This vulnerability is classified under CWE-502 (Deserialization of Untrusted Data), a well-known vulnerability class that occurs when applications deserialize data from untrusted sources without proper validation. In the context of Microsoft Office, the deserialization flaw can be triggered locally, requiring user interaction to exploit. The scope of impact extends beyond the vulnerable component itself, potentially affecting the confidentiality, integrity, and availability of the broader system.

The attack requires local access to the target system but does not require any prior privileges, making it accessible to any user who can execute code on the machine. User interaction is required, typically through opening a malicious document or interacting with crafted content.

Root Cause

The root cause of CVE-2025-47994 lies in the improper deserialization of untrusted data within Microsoft Office components. When Office processes certain serialized objects, it fails to adequately validate the integrity and source of the data being deserialized. This allows an attacker to craft malicious serialized payloads that, when processed by the application, can instantiate arbitrary objects and execute code in the context of the Office application, subsequently leading to privilege escalation.

Attack Vector

The attack vector is local, meaning the attacker must have access to the target system to exploit this vulnerability. The typical attack scenario involves:

1. An attacker crafts a malicious Office document containing specially crafted serialized data
2. A user on the target system opens the malicious document
3. Microsoft Office deserializes the untrusted data without proper validation
4. The deserialization process instantiates malicious objects that execute attacker-controlled code
5. The attacker gains elevated privileges on the local system

The vulnerability is particularly dangerous because it can bypass security boundaries and affect components beyond the initially vulnerable Office application, as indicated by the changed scope in the vulnerability assessment.

Detection Methods for CVE-2025-47994

Indicators of Compromise

• Unexpected child processes spawned by Microsoft Office applications (WINWORD.EXE, EXCEL.EXE, POWERPNT.EXE)
• Anomalous file system or registry modifications initiated by Office processes
• Unusual network connections or system calls originating from Office applications
• Presence of suspicious Office documents with embedded serialized objects

Detection Strategies

• Monitor process creation events for Office applications spawning unexpected child processes such as cmd.exe, powershell.exe, or other scripting interpreters
• Implement application whitelisting to detect unauthorized code execution from Office process contexts
• Deploy endpoint detection rules that identify deserialization attack patterns in Office document structures
• Enable enhanced logging for Office applications to capture detailed execution telemetry

Monitoring Recommendations

• Configure SIEM rules to alert on privilege escalation attempts following Office document interactions
• Monitor Windows Event Logs for suspicious process token manipulation events
• Implement file integrity monitoring on Office installation directories
• Track macro execution and embedded object activation within Office documents

How to Mitigate CVE-2025-47994

Immediate Actions Required

• Apply the latest security updates from Microsoft for all affected Office products immediately
• Enable Protected View for documents from untrusted sources across all Office applications
• Restrict macro execution using Group Policy to prevent unauthorized code execution
• Implement application control policies to limit Office applications from spawning child processes

Patch Information

Microsoft has released security updates to address this vulnerability. Organizations should apply patches through the standard Microsoft Update channels or Windows Server Update Services (WSUS). Detailed patch information and guidance is available in the Microsoft Security Response Center Advisory.

For enterprise deployments, administrators should prioritize patching Microsoft 365 Apps, Office 2016, Office 2019, Office LTSC 2021/2024, and SharePoint Enterprise Server 2016 installations.

Workarounds

• Enable Attack Surface Reduction (ASR) rules to block Office applications from creating child processes
• Configure Office applications to run in Protected View mode by default for all documents
• Disable Trust Center settings that allow automatic execution of embedded content
• Implement network segmentation to limit the impact of potential privilege escalation

# Enable ASR rule to block Office apps from creating child processes
# Run in elevated PowerShell
Set-MpPreference -AttackSurfaceReductionRules_Ids d4f940ab-401b-4efc-aadc-ad5f3c50688a -AttackSurfaceReductionRules_Actions Enabled

# Verify ASR rule is enabled
Get-MpPreference | Select-Object -ExpandProperty AttackSurfaceReductionRules_Ids