CVE-2025-49703 Overview
CVE-2025-49703 is a use-after-free vulnerability [CWE-416] in Microsoft Office Word that allows an unauthorized attacker to execute code locally. The flaw affects multiple Microsoft Office products including Microsoft 365 Apps, Office 2019, Office Long Term Servicing Channel (LTSC) 2021 and 2024, Word 2016, and SharePoint Server 2016/2019. Exploitation requires user interaction, typically opening a crafted Word document. Successful exploitation grants attacker-controlled code execution in the context of the current user, leading to compromise of confidentiality, integrity, and availability on the affected host.
Critical Impact
An attacker can achieve arbitrary code execution on a victim system by convincing a user to open a malicious Word document, with no authentication required and no need for elevated privileges.
Affected Products
- Microsoft 365 Apps (Enterprise, x64 and x86)
- Microsoft Office 2019, Office LTSC 2021, Office LTSC 2024 (Windows and macOS)
- Microsoft Word 2016 and Microsoft SharePoint Server 2016/2019
Discovery Timeline
- 2025-07-08 - CVE-2025-49703 published to the National Vulnerability Database (NVD)
- 2025-07-16 - Last updated in NVD database
Technical Details for CVE-2025-49703
Vulnerability Analysis
The vulnerability is a use-after-free condition in Microsoft Office Word's document processing logic. Use-after-free flaws occur when a program continues to reference memory after that memory has been freed. An attacker who controls the contents of a Word document can manipulate object lifetimes during parsing to trigger access to a freed object. Reallocating that memory region with attacker-controlled data enables hijacking of execution flow, typically through corruption of a virtual function pointer or callback structure.
The attack requires local access and user interaction, meaning the victim must open the malicious file. The EPSS probability is 1.107% (78.354 percentile), indicating elevated exploitation likelihood relative to the broader CVE population. No public proof-of-concept exploit has been published, and the vulnerability is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Root Cause
The root cause is improper handling of object lifetime within Word's document parser. A specific document construct causes Word to free an internal object while retaining a dangling pointer to it. Subsequent operations dereference the freed pointer, allowing attacker-controlled heap contents to be interpreted as a valid object. Microsoft has not released technical specifics about the affected component beyond the MSRC advisory.
Attack Vector
Attackers deliver a weaponized .doc or .docx file through phishing email, malicious download, or compromised file share. When the user opens the document, Word processes the malicious structure and triggers the use-after-free. SharePoint Server is also affected because it processes Office documents server-side via shared Office libraries. The Preview Pane is not confirmed as an attack vector for this CVE in vendor documentation. See the Microsoft CVE-2025-49703 Advisory for vendor-supplied details.
Detection Methods for CVE-2025-49703
Indicators of Compromise
- Unexpected child processes spawned from winword.exe or WINWORD.EXE, such as cmd.exe, powershell.exe, rundll32.exe, or mshta.exe
- Word process crashes followed by suspicious binary writes to %APPDATA%, %TEMP%, or %LOCALAPPDATA%
- Outbound network connections initiated by winword.exe to untrusted external hosts
- Office documents arriving from external senders containing unusual embedded objects, OLE streams, or template-injection references
Detection Strategies
- Monitor for anomalous process trees where Microsoft Office binaries spawn script interpreters or living-off-the-land binaries (LOLBins).
- Inspect inbound email attachments and SharePoint uploads for Word documents containing malformed structures and known exploit primitives.
- Apply behavioral analytics that correlate Office application crashes with subsequent suspicious file or registry writes.
Monitoring Recommendations
- Enable Microsoft Defender Attack Surface Reduction (ASR) rules that block Office applications from creating child processes and writing executable content.
- Forward Sysmon Event IDs 1 (process creation), 7 (image load), and 11 (file create) from endpoints running Office to a centralized analytics platform.
- Audit SharePoint server logs for document upload and rendering activity that triggers worker process faults.
How to Mitigate CVE-2025-49703
Immediate Actions Required
- Apply the July 2025 Microsoft security updates to all affected Office, Microsoft 365 Apps, Word, and SharePoint Server installations.
- Verify Microsoft 365 Apps clients are receiving updates through Click-to-Run and confirm build versions match the patched release.
- Restrict opening of Word documents from untrusted sources and enforce Protected View for files originating from the internet or email.
Patch Information
Microsoft addressed CVE-2025-49703 through security updates referenced in the Microsoft CVE-2025-49703 Advisory. Administrators should consult the MSRC update guide for the specific KB numbers and build versions applicable to each product channel, including Microsoft 365 Apps, Office 2019, Office LTSC 2021/2024, Word 2016, and SharePoint Server 2016/2019.
Workarounds
- Configure Group Policy to enforce Protected View and disable editing for documents from the internet, unsafe locations, and Outlook attachments.
- Enable Microsoft Defender Attack Surface Reduction rules that block child process creation from Office applications.
- Use File Block policy to prevent legacy Word binary formats from opening until patches are applied across the estate.
- Train users to report unexpected document prompts and avoid disabling Protected View when prompted by untrusted files.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
