CVE-2018-9953 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit Reader 9.0.1.1049. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the XFA resolveNodes method of Button elements. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code under the context of the current process. Was ZDI-CAN-5528.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2018-9953 represents a critical remote code execution flaw affecting Foxit Reader version 9.0.1.1049, demonstrating a classic object-oriented programming error that has significant implications for document security. This vulnerability resides within the XFA (XML Forms Architecture) processing functionality of the PDF reader, specifically within the resolveNodes method of Button elements, making it particularly dangerous as it can be triggered through standard PDF document interactions. The flaw constitutes a direct violation of secure coding practices, as it fails to validate object existence before performing operations on potentially invalid references, creating a pathway for malicious code injection.
The technical nature of this vulnerability aligns with CWE-476, which describes "NULL Pointer Dereference" conditions where a null pointer is dereferenced without proper validation. This particular implementation flaw occurs during the XFA form processing phase when the application attempts to resolve nodes within Button elements without first confirming that these objects exist or are properly initialized. When a malicious PDF document contains crafted XFA content with malformed Button elements, the reader's processing engine encounters a null reference that leads to arbitrary code execution. The vulnerability requires user interaction through visiting a malicious webpage or opening a malicious file, which makes it particularly insidious as it can be delivered through social engineering campaigns or compromised websites.
The operational impact of CVE-2018-9953 extends beyond simple code execution, as the attacker can operate under the privileges of the currently running Foxit Reader process, potentially compromising the entire system. This vulnerability provides attackers with a persistent foothold that can be leveraged for further exploitation, including privilege escalation, data exfiltration, or deployment of additional malware. The attack vector through web browsing or file opening makes this vulnerability particularly dangerous in enterprise environments where users frequently interact with PDF documents from untrusted sources. The vulnerability's classification as a remote code execution flaw places it within the ATT&CK framework's T1203 (Exploitation for Client Execution) technique category, demonstrating how attackers can exploit software vulnerabilities to execute malicious code on target systems.
Security researchers have identified this vulnerability as part of the broader landscape of PDF reader exploits that target the XFA processing functionality, which has historically been a weak point in PDF rendering engines due to the complexity of XML-based form processing. The vulnerability's exploitation requires minimal user interaction, making it particularly effective for phishing campaigns or drive-by download attacks where users are tricked into opening malicious documents. Organizations should implement immediate mitigations including updating to patched versions of Foxit Reader, implementing web filtering solutions to block malicious PDF content, and conducting user awareness training to recognize suspicious document attachments. The vulnerability also highlights the importance of input validation and proper error handling in complex document processing systems, as proper validation of object references could have prevented the null pointer dereference condition that leads to arbitrary code execution.