CVE-2017-14823 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit Reader 8.3.1.21155. 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 signer method of XFA's Signature objects. The issue results from the lack of proper validation of user-supplied data, which can result in a type confusion condition. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-5015.
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Analysis
by VulDB Data Team • 12/16/2019
CVE-2017-14823 represents a critical remote code execution vulnerability affecting Foxit Reader version 8.3.1.21155 that demonstrates a classic type confusion flaw within the XFA signature object handling mechanism. This vulnerability operates under the Common Weakness Enumeration category CWE-471, which specifically addresses the issue of incorrect behavior in the handling of data types during program execution. The flaw manifests in the signer method of XML Forms Architecture (XFA) signature objects where insufficient input validation permits attackers to manipulate data types in ways that trigger unexpected program behavior. The vulnerability requires user interaction to exploit, meaning victims must either visit a malicious web page or open a specially crafted malicious file containing the vulnerable XFA signature object. This attack vector aligns with the MITRE ATT&CK framework's technique T1203, which describes exploitation of software vulnerabilities through user interaction, typically via malicious documents or web content. The type confusion condition occurs when the application fails to properly validate the data types of user-supplied inputs, allowing an attacker to craft malicious payloads that cause the program to interpret data as different types than intended. When this occurs in the context of XFA signature processing, the type confusion can lead to memory corruption and arbitrary code execution within the context of the currently running Foxit Reader process, effectively providing attackers with the same privileges as the legitimate user. The exploitation process leverages the fact that XFA signatures are designed to validate document integrity through cryptographic means, but the implementation fails to properly validate the structure and content of these signature objects. This vulnerability essentially allows an attacker to bypass normal execution flow controls and inject malicious code that executes with the privileges of the Foxit Reader application, potentially enabling full system compromise if the application has elevated permissions.
The security implications of CVE-2017-14823 extend beyond simple code execution as it represents a fundamental flaw in the application's input handling and type management mechanisms. The vulnerability's classification under CWE-471 indicates that it involves a specific pattern of type confusion where the program's type checking mechanism fails to properly validate data types before processing them. This type of vulnerability is particularly dangerous because it can be exploited remotely without requiring any authentication or privileged access. The fact that the vulnerability exists within the XFA signature handling code path makes it especially concerning since XFA forms are commonly used in business documents and PDF files that users frequently open. The attack surface is broadened by the fact that malicious XFA signatures can be embedded in various document formats that Foxit Reader supports, including PDF files that might be received via email, downloaded from websites, or shared through collaborative platforms. When an attacker successfully exploits this vulnerability, they can execute arbitrary code on the target system with the privileges of the Foxit Reader process, which typically runs with the same privileges as the user who opened the document. This creates a pathway for further attacks, including privilege escalation, data exfiltration, or the installation of additional malicious software. The vulnerability's exploitation requires the user to interact with the malicious content, which makes it particularly challenging to defend against through automated means, as it relies on social engineering aspects of the attack.
Mitigation strategies for CVE-2017-14823 should focus on both immediate remediation and long-term defensive measures. The most effective immediate solution is to upgrade to a patched version of Foxit Reader, as this vulnerability was addressed in subsequent releases. Organizations should implement comprehensive patch management procedures to ensure all instances of vulnerable software are updated promptly. The vulnerability also highlights the importance of input validation and type checking in application security, making it a prime example of why defensive programming practices should be rigorously enforced. Security teams should implement content filtering measures that can detect and block malicious XFA signatures or potentially harmful PDF content before it reaches end users. Network-based security controls such as web proxies, email filters, and intrusion detection systems can be configured to identify and block known malicious patterns associated with this vulnerability. The attack pattern described in CVE-2017-14823 also demonstrates the need for application whitelisting and sandboxing techniques, where applications are restricted to executing only trusted code and content. From a monitoring perspective, organizations should implement behavioral analysis systems that can detect anomalous execution patterns or memory corruption indicators that might suggest exploitation attempts. The vulnerability's classification under ATT&CK technique T1203 emphasizes the importance of user education and awareness programs to help prevent successful social engineering attacks that leverage this vulnerability. Additionally, security professionals should consider implementing automated vulnerability scanning tools that can identify and report on the presence of vulnerable applications within their environments, ensuring that all instances of Foxit Reader are properly updated and patched against this specific type confusion vulnerability.