CVE-2025-24057: Microsoft 365 Apps Buffer Overflow Flaw

CVE-2025-24057 Overview

CVE-2025-24057 is a heap-based buffer overflow vulnerability affecting Microsoft Office products that allows an unauthorized attacker to execute arbitrary code locally. This memory corruption flaw occurs when Office applications improperly handle specially crafted input, enabling attackers to overwrite heap memory and potentially gain control of the affected system. Successful exploitation requires user interaction, typically through opening a malicious document.

Critical Impact

Attackers can achieve arbitrary code execution on vulnerable systems by exploiting improper memory handling in Microsoft Office, potentially leading to complete system compromise, data theft, or ransomware deployment.

Affected Products

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

Discovery Timeline

• 2025-03-11 - CVE-2025-24057 published to NVD
• 2025-07-02 - Last updated in NVD database

Technical Details for CVE-2025-24057

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a dangerous memory corruption flaw that occurs when data is written beyond the boundaries of an allocated heap buffer. In the context of Microsoft Office, this typically manifests during the parsing of document content where insufficient bounds checking allows an attacker to corrupt adjacent heap memory structures.

The exploitation scenario requires local access and user interaction—specifically, an attacker must convince a user to open a maliciously crafted Office document. Once opened, the heap overflow can be leveraged to corrupt function pointers or other critical data structures, ultimately redirecting execution flow to attacker-controlled code. This grants the attacker the same privileges as the compromised user, enabling full compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The vulnerability stems from improper validation of input data during document processing operations within Microsoft Office. When parsing certain document elements, the application fails to adequately verify that input data fits within allocated heap buffers. This boundary validation failure allows attackers to craft documents containing oversized or malformed data that exceeds buffer limits, resulting in heap memory corruption that can be weaponized for code execution.

Attack Vector

The attack vector is local, requiring an attacker to deliver a malicious Office document to the target user. Common delivery mechanisms include:

• Phishing emails with malicious document attachments
• Documents hosted on compromised or attacker-controlled websites
• Social engineering to convince users to open shared documents

Once the victim opens the malicious document, the heap overflow is triggered during document parsing. The attacker can craft the overflow to overwrite heap metadata or adjacent objects, potentially achieving arbitrary code execution. No authentication is required for exploitation, but user interaction (opening the document) is mandatory.

The vulnerability manifests during heap memory operations when processing Office documents. When a specially crafted document is opened, the application allocates a heap buffer for document content but fails to properly validate the size of incoming data. An attacker can construct a document where the payload size exceeds the allocated buffer, causing a write operation beyond the buffer boundary. This heap corruption can be leveraged to overwrite adjacent heap structures or function pointers, enabling code execution with the privileges of the Office application. For detailed technical information, refer to the Microsoft Security Update Guide.

Detection Methods for CVE-2025-24057

Indicators of Compromise

• Unexpected crashes or hangs of Microsoft Office applications (Word, Excel, PowerPoint) when opening documents
• Office applications spawning unusual child processes such as cmd.exe, powershell.exe, or mshta.exe
• Suspicious document files with unusual internal structures or embedded content arriving via email
• Anomalous memory allocation patterns or heap corruption errors in Windows Event logs

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions like SentinelOne to monitor for heap exploitation techniques and suspicious process behavior
• Implement email security gateways to scan and sandbox Office document attachments before delivery
• Configure Windows Defender Exploit Guard with Attack Surface Reduction (ASR) rules for Office applications
• Enable Protected View and Application Guard for Office to isolate potentially malicious documents

Monitoring Recommendations

• Monitor Office application process creation events for unexpected child processes
• Track document opens from untrusted locations (email attachments, downloads, network shares)
• Implement file integrity monitoring for Office installation directories
• Review crash dumps from Office applications for signs of heap corruption or exploitation attempts

How to Mitigate CVE-2025-24057

Immediate Actions Required

• Apply Microsoft security updates immediately for all affected Office installations
• Enable Protected View in Microsoft Office to open documents from untrusted sources in a sandboxed environment
• Block or quarantine Office documents from untrusted sources at the email gateway level
• Educate users about phishing risks and the dangers of opening unexpected document attachments

Patch Information

Microsoft has released security updates to address this vulnerability. Organizations should apply patches through their standard update mechanisms:

• Microsoft 365 Apps: Update through Microsoft Update or Configuration Manager
• Office 2016/2019: Apply the corresponding cumulative update from Microsoft Update Catalog
• Office LTSC 2021/2024: Deploy updates via WSUS, SCCM, or direct download

For complete patch details and download links, refer to the Microsoft Security Update Guide for CVE-2025-24057.

Workarounds

• Enable Protected View for files originating from the Internet, unsafe locations, and Outlook attachments
• Configure Microsoft Defender Application Guard for Office to open untrusted documents in an isolated container
• Restrict macro execution and embedded content in Office documents through Group Policy
• Implement network segmentation to limit lateral movement if a workstation is compromised

# Enable Protected View settings via Group Policy (Registry)
# For files from the Internet
reg add "HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableInternetFilesInPV /t REG_DWORD /d 0 /f
# For files in unsafe locations
reg add "HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableUnsafeLocationsInPV /t REG_DWORD /d 0 /f
# For Outlook attachments
reg add "HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableAttachmentsInPV /t REG_DWORD /d 0 /f