CVE-2018-9956 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 handling of XFA Button elements. When setting the title attribute, the process does not properly validate 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-5617.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2018-9956 represents a critical remote code execution flaw in Foxit Reader version 9.0.1.1049 that demonstrates a classic improper validation of input prior to object access pattern. This issue resides within the XFA (XML Forms Architecture) button element processing functionality where the application fails to validate whether an object exists before attempting operations on it. The vulnerability manifests when the title attribute of an XFA button element is set, creating a condition where uninitialized or improperly validated objects can be manipulated to trigger arbitrary code execution. This flaw operates under the broader category of CWE-476 which encompasses null pointer dereferences and improper object validation scenarios, making it particularly dangerous as it can be exploited without requiring administrative privileges or special user permissions beyond normal document interaction.
The technical exploitation of this vulnerability requires user interaction through either visiting a malicious webpage or opening a malicious PDF file containing specifically crafted XFA button elements. When the vulnerable Foxit Reader processes such documents, the application's XFA parser encounters the malformed title attribute and proceeds with operations on an object that has not been properly validated or instantiated. This creates a scenario where memory corruption can occur, potentially allowing attackers to inject and execute malicious code within the context of the currently running Foxit Reader process. The vulnerability's impact is significant as it can be leveraged to bypass standard security controls and execute arbitrary commands on affected systems, making it a prime target for attackers seeking to compromise user workstations through document-based attacks.
From an operational perspective, this vulnerability presents a substantial risk to organizations relying on Foxit Reader for document processing, as it can be exploited through social engineering tactics such as phishing emails containing malicious PDF attachments or compromised websites hosting malicious content. The requirement for user interaction makes it less likely to be exploited at scale compared to fully automated vulnerabilities, but it remains highly dangerous in targeted attacks where attackers can convince users to interact with malicious content. The vulnerability's exploitation chain involves multiple steps including document delivery, user interaction, and code execution within the application's memory space, with the attack surface expanding to include web browsers, email clients, and any system where Foxit Reader is installed and configured to automatically open PDF documents. This aligns with ATT&CK technique T1203 which covers exploitation of remote services and T1059 which involves command and script interpreters, demonstrating how this vulnerability can be used to establish persistent access or escalate privileges.
Organizations should implement immediate mitigations including updating to the latest version of Foxit Reader where this vulnerability has been patched, implementing strict document filtering policies to prevent execution of potentially malicious PDF files, and deploying network-based intrusion detection systems that can identify suspicious PDF content patterns. Security teams should also consider implementing application whitelisting controls to restrict execution of Foxit Reader from untrusted sources and configure automatic updates for all vulnerable software components. The vulnerability's classification under CWE-476 and its exploitation patterns align with industry best practices for vulnerability management and incident response, emphasizing the importance of maintaining up-to-date software patches and implementing defense-in-depth strategies that include multiple layers of protection against document-based attacks. Additionally, user education programs should be enhanced to raise awareness about the risks of opening unexpected PDF files or visiting untrusted websites that may contain malicious content designed to exploit such vulnerabilities.