CVE-2025-47957: Microsoft Word Remote Code Execution Vulnerability
Description
CVE-2025-47957 is a critical "use after free" vulnerability in Microsoft Office Word. It allows an unauthorized attacker to execute code locally on the affected machine. The flaw arises when Microsoft Word mistakenly continues to reference memory after it has been released (“freed”). If an attacker can manipulate what gets written to this freed memory—typically by tricking a user into opening a specially crafted Word document—they can inject and run their own code in the security context of the user running Word.Technical Overview
- Vulnerability Class: Use-after-free (UAF) memory bug.
- Exploit Mechanism: The attacker sends a malicious document to the target. When opened in a vulnerable Word installation, Word attempts to access already-freed memory, which can now hold attacker-controlled code or pointers.
- Effect: Can result in arbitrary code execution with the user’s privileges. Depending on the user’s rights, this may allow installation of malware, further exploitation, privilege escalation, or data exfiltration.
Attack Scenario
- The attacker creates a crafted Office document (Word .doc/.docx) designed to trigger the UAF flaw.
- Delivery can occur via phishing emails, malicious websites, or cloud sharing.
- If the user opens the document and disables security warnings (like Protected View), exploitation is triggered, leading to code execution.
Security and Business Impact
- Local Code Execution: Even though this is a "local" vulnerability, it is commonly exploited via remote vectors such as email attachments.
- Enterprise Risk: Once local code execution is achieved, attackers may pivot to broader enterprise network compromise, privilege escalation, and persistent malware infection.
- Privileged Execution: The exploit inherits the privileges of the Word process. If the victim is an administrator, the entire system could be compromised.
Mitigation and Best Practices
- Patch Promptly: Microsoft has committed to patching this vulnerability in upcoming security updates. Expedite patch deployment once available.
- Protected View: Keep Word’s Protected View enabled. Opening documents from untrusted sources in this sandbox mode reduces risk.
- Macro Restriction: Limit or disable macros except for trusted workflows; macros are a common vector for document-based exploits.
- User Training: Educate users not to open unknown or unexpected attachments, and to beware of phishing or social engineering attempts.
- Endpoint Security: Deploy up-to-date antivirus and endpoint detection and response (EDR) solutions. Monitor for suspicious Word activity (e.g., spawning PowerShell or suspicious outbound traffic).
- Least Privilege: Users should operate with the least necessary permissions to reduce exploit impact.
- Application Whitelisting: Limit which executables and scripts can run to block unauthorized payload execution.
- Regular Audits: Routinely review system and application logs for signs of anomaly or exploitation.
Additional Notes
- Multiple versions of Microsoft Office are typically impacted (Office 2019, 2021, Microsoft 365 desktop apps, Office LTSC); Office Online is not vulnerable due to the attack vector requiring client-side memory access.
- This class of vulnerabilities is historically significant: similar memory management flaws have enabled attacks like Follina and other high-profile Office exploits in the past.
- The vulnerability may also bypass some mitigations like DEP/ASLR if targeted precisely, further underlining the need for prompt patching and multi-layered security.
Bottom Line:
CVE-2025-47957 is a critical risk for all Microsoft Office Word users, especially in enterprise environments. Prompt patching, user vigilance, maintaining robust security configurations, and multi-layered defenses are essential to mitigate exploitation risk.
Source: MSRC Security Update Guide - Microsoft Security Response Center
