CVE-2018-9966 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 Calculate actions of TextBox objects. 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-5570.
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Analysis
by VulDB Data Team • 08/15/2024
This vulnerability in Foxit Reader 9.0.1.1049 represents a critical remote code execution flaw that demonstrates poor input validation and object lifecycle management in PDF processing software. The vulnerability specifically affects the handling of Calculate actions within TextBox objects, where the application fails to validate whether referenced objects exist before attempting operations on them. This fundamental flaw creates a condition where an attacker can craft malicious PDF files that trigger unintended code execution when processed by the vulnerable reader. The issue falls under CWE-476 which defines "NULL Pointer Dereference" as the underlying weakness, where the application assumes object existence without proper validation. The vulnerability requires user interaction to exploit, making it a client-side attack vector that relies on social engineering to deliver malicious content through web pages or file attachments. This attack pattern aligns with ATT&CK technique T1203 which describes "Exploitation for Client Execution" where adversaries leverage application vulnerabilities to execute code on victim systems.
The technical implementation of this vulnerability exploits the lack of proper object validation during PDF parsing operations, particularly when processing Calculate actions associated with interactive form elements. When Foxit Reader encounters a TextBox object with a Calculate action, it attempts to access and manipulate referenced objects without first verifying their existence in memory. This creates a predictable execution path where crafted malicious input can cause the application to dereference null or invalid pointers, leading to arbitrary code execution. The vulnerability operates at the application level within the PDF rendering engine, specifically targeting the form field processing subsystem. Attackers can leverage this by embedding malicious JavaScript or other executable content within PDF files, which gets executed when the vulnerable reader processes the Calculate action. The execution context is limited to the privileges of the current process, meaning successful exploitation would allow attackers to perform actions with the same permissions as the Foxit Reader application itself.
The operational impact of this vulnerability extends beyond simple code execution to potentially enable full system compromise through subsequent attack vectors. Since the vulnerability requires user interaction, attackers can employ phishing campaigns or drive-by downloads to deliver malicious PDF files that exploit this weakness. The attack surface is significant given that Foxit Reader is widely used for viewing PDF documents across enterprise and individual environments, making it an attractive target for threat actors. Organizations using vulnerable versions of Foxit Reader face risks including data exfiltration, persistent backdoor installation, and lateral movement within networks. The vulnerability's classification as a remote code execution flaw means that attackers need not have physical access to target systems, making it particularly dangerous in enterprise environments where PDF documents are frequently shared. The issue also highlights the importance of proper sandboxing and input validation in document processing applications, as the vulnerability stems from inadequate defensive programming practices.
Mitigation strategies for this vulnerability should focus on immediate remediation through official patches provided by Foxit Corporation, as well as implementing network-based protections to prevent access to known malicious PDF content. Organizations should deploy web application firewalls and content filtering solutions that can detect and block suspicious PDF file downloads or embedded JavaScript. The vulnerability can be addressed through user education to avoid opening PDF files from untrusted sources, combined with endpoint protection measures that monitor for suspicious process behavior. Additionally, administrators should consider implementing application whitelisting policies that restrict execution of unauthorized code within the PDF processing environment. The fix should include proper object validation before any operations are performed on referenced elements, implementing checks that ensure object existence and proper initialization before access. Security teams should also monitor for indicators of compromise related to this vulnerability, including unusual network connections or file access patterns that may indicate exploitation attempts. Regular security assessments of document processing applications should be conducted to identify similar validation weaknesses in other software components.