CVE-2021-38656 in Word
Summary
by MITRE • 09/15/2021
Microsoft Word Remote Code Execution Vulnerability
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/17/2021
Microsoft Word contains a remote code execution vulnerability that arises from improper handling of specially crafted Office Open XML files. This vulnerability specifically affects the way Word processes certain elements within .docx documents, particularly when dealing with embedded objects and complex formatting structures. The flaw exists in the document parsing logic that fails to properly validate input data before executing associated code paths. Attackers can exploit this vulnerability by crafting malicious Word documents that contain malformed Office Open XML elements designed to trigger buffer overflows or arbitrary code execution within the Word application process. The vulnerability is particularly dangerous because it can be triggered through normal document opening procedures without requiring any special user interaction beyond opening the malicious file. According to CWE-121, this represents a classic stack-based buffer overflow condition where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The ATT&CK framework categorizes this under T1203, which involves legitimate user interaction to execute malicious code, and T1059, covering command and scripting interpreter usage. This vulnerability impacts multiple versions of Microsoft Word including Office 2016, Office 2019, and Office 2021, making it a widespread concern across enterprise environments. The remote code execution capability allows attackers to gain full control of the affected system, potentially leading to data exfiltration, persistence mechanisms, or further network exploitation. The vulnerability is particularly concerning because it can be exploited through various attack vectors including email attachments, web downloads, or malicious Office documents shared through collaboration platforms. Microsoft has addressed this issue through security updates that enhance input validation and implement additional memory protection mechanisms. Organizations should prioritize patching this vulnerability immediately, as it represents a critical threat to enterprise security infrastructure. The exploitability of this vulnerability is relatively high due to the widespread use of Microsoft Word in corporate environments and the minimal user interaction required to trigger the malicious code execution. Security teams should monitor for suspicious document opening activities and implement additional email filtering measures to prevent delivery of potentially malicious Office documents to end users. The vulnerability also highlights the importance of maintaining up-to-date security patches across all Microsoft Office applications, as similar issues may exist in other components of the Office suite that handle similar document formats.