CVE-2018-9957 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 parsing arguments passed to the resetData method, 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-5618.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2018-9957 represents a critical remote code execution flaw in Foxit Reader version 9.0.1.1049 that demonstrates the dangerous consequences of improper object validation in PDF processing applications. This vulnerability falls under the CWE-476 category of NULL Pointer Dereference, where the application fails to verify that an object reference is valid before attempting to access its properties or methods. The flaw specifically manifests during the parsing of XFA (XML Forms Architecture) Button elements within PDF documents, making it particularly insidious as it can be triggered through standard PDF document rendering processes that users encounter when opening files or visiting web pages containing malicious content.
The technical implementation of this vulnerability stems from the improper validation of object references within the resetData method of XFA button elements. When Foxit Reader processes a PDF document containing malicious XFA content, the application attempts to parse arguments passed to the resetData method without first confirming whether the target object exists or has been properly initialized. This lack of validation creates a condition where a null pointer dereference can occur, allowing an attacker to manipulate the execution flow of the application. The vulnerability is particularly dangerous because it operates within the context of the currently running process, meaning that successful exploitation can result in arbitrary code execution with the privileges of the Foxit Reader application itself. This represents a significant escalation from the typical sandboxing limitations that PDF readers implement to protect users from malicious content.
From an operational perspective, this vulnerability creates a substantial risk for organizations that rely on Foxit Reader for document processing, as it requires only user interaction to exploit through either visiting a malicious webpage or opening a compromised PDF file. The attack vector aligns with common phishing techniques and malicious document delivery methods that have been prevalent in enterprise security threats. Security professionals should recognize this vulnerability as part of the broader ATT&CK framework's T1203 - Exploitation for Client Execution category, where adversaries leverage application vulnerabilities to execute code on target systems. The impact extends beyond individual user compromise to potentially affect entire organizational networks, especially in environments where Foxit Reader is widely deployed and users regularly open PDF documents from untrusted sources.
Organizations should implement immediate mitigations including updating to the latest version of Foxit Reader that addresses this vulnerability, which typically involves patching the XFA parsing logic to include proper null pointer validation. Network-based protections such as web application firewalls and PDF content filtering systems can provide additional layers of defense by scanning incoming PDF documents for suspicious XFA elements. Security teams should also consider implementing user education programs to reduce the likelihood of successful exploitation through social engineering tactics that encourage users to avoid visiting untrusted websites or opening suspicious PDF attachments. The vulnerability serves as a reminder of the importance of proper input validation in security-critical applications and demonstrates how seemingly minor flaws in object handling can lead to severe remote code execution capabilities that compromise entire systems.