CVE-2018-8430 in Word
Summary
by MITRE
A remote code execution vulnerability exists in Microsoft Word if a user opens a specially crafted PDF file, aka "Word PDF Remote Code Execution Vulnerability." This affects Microsoft Word, Microsoft Office.
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Analysis
by VulDB Data Team • 05/08/2023
The vulnerability identified as CVE-2018-8430 represents a critical remote code execution flaw in Microsoft Word applications that specifically manifests when users open maliciously crafted PDF files. This vulnerability exploits the interaction between Word's PDF handling capabilities and the underlying document processing engine, creating a pathway for attackers to execute arbitrary code on affected systems. The flaw exists within Microsoft Office's integrated PDF rendering functionality, which allows Word to display PDF documents without requiring separate PDF reader applications. This design decision, while convenient for users, introduces a significant attack surface that malicious actors can leverage to compromise systems. The vulnerability affects multiple versions of Microsoft Word including Office 2007, 2010, 2013, 2016, and Office 2019, as well as Office 2016 for Mac, making it particularly dangerous given the widespread adoption of these applications across enterprise environments.
The technical root cause of this vulnerability stems from insufficient input validation and memory corruption issues within Word's PDF processing components. When a user opens a specially crafted PDF file, the malicious document contains malformed data structures or embedded code that triggers buffer overflows or memory corruption conditions within the Word application. This occurs during the PDF parsing and rendering process where Word attempts to interpret and display PDF elements such as embedded objects, JavaScript code, or malformed metadata. The vulnerability is classified as a heap-based buffer overflow according to CWE-129, which represents an insufficient validation of the length of user-supplied data before processing. Attackers can exploit this by crafting PDF files that contain oversized data structures or malformed entries that exceed the allocated memory boundaries, causing the application to execute malicious code with the privileges of the current user. The flaw operates at the application layer and requires only a single interaction from the user to trigger the exploit, making it particularly dangerous in phishing campaigns or targeted attacks.
The operational impact of CVE-2018-8430 extends far beyond simple remote code execution, as it provides attackers with a complete foothold for further compromise within affected networks. Successful exploitation allows threat actors to install malware, steal sensitive data, establish persistence mechanisms, or launch lateral movement attacks against other systems. The vulnerability can be leveraged to bypass traditional security controls since it operates within legitimate application boundaries and may not trigger typical network-based intrusion detection systems. Organizations running affected versions of Microsoft Office are at risk of sophisticated attacks where the initial compromise occurs through social engineering tactics targeting end users to open malicious PDF attachments. The vulnerability's characteristics align with ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries use legitimate application software to execute malicious code. Additionally, the flaw can be combined with other techniques such as T1059 - Command and Scripting Interpreter, enabling attackers to establish command and control channels and maintain persistent access to compromised systems.
Mitigation strategies for CVE-2018-8430 must address both immediate defensive measures and long-term architectural improvements to protect against similar vulnerabilities. Microsoft released security updates that patch the vulnerability by implementing proper input validation and memory management controls within the PDF processing components of Word applications. Organizations should prioritize immediate deployment of the relevant security patches, which are available through Microsoft's Update Catalog and Windows Update services. Beyond patching, network administrators should implement additional protective measures such as disabling PDF file handling within Word applications, using application whitelisting solutions, and implementing email filtering rules that block suspicious PDF attachments. The vulnerability highlights the importance of principle of least privilege and user education initiatives to reduce the risk of successful exploitation through social engineering attacks. Security teams should also consider implementing endpoint detection and response solutions that can identify anomalous behavior patterns associated with exploitation attempts, such as unexpected process creation or memory allocation patterns. Organizations should conduct regular vulnerability assessments to identify and remediate similar issues in other Microsoft Office components and third-party applications that may present similar attack vectors. The incident underscores the necessity of maintaining current security practices and the importance of understanding how integrated application features can create unexpected security risks when not properly secured.