CVE-2018-9936 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit Reader 9.0.0.29935. 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 parsing of field elements. 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 under the context of the current process. Was ZDI-CAN-5370.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2018-9936 represents a critical security flaw in Foxit Reader version 9.0.0.29935 that enables remote code execution through a type confusion condition. This vulnerability resides within the PDF parsing functionality of the software, specifically in how the application handles field elements during document processing. The flaw stems from insufficient input validation mechanisms that fail to properly sanitize user-supplied data, creating an environment where malicious actors can manipulate the parsing behavior to achieve unauthorized code execution. The vulnerability operates at the intersection of multiple security domains, including memory corruption and privilege escalation, making it particularly dangerous for end users who may unknowingly encounter malicious content.
The technical root cause of this vulnerability aligns with CWE-415 which describes improper handling of memory allocation and deallocation, and CWE-471 which addresses the failure to properly validate input data. The type confusion condition occurs when the application incorrectly interprets the data type of certain field elements within PDF documents, leading to memory corruption that can be exploited to redirect execution flow. This condition typically manifests when the parser encounters malformed or specially crafted field elements that cause the application to treat memory locations as different data types than originally intended. The vulnerability requires user interaction to be exploited, meaning victims must either visit a malicious webpage hosting a crafted PDF or open a malicious file directly, making it a client-side attack vector that leverages social engineering tactics.
From an operational perspective, this vulnerability presents significant risk to organizations relying on Foxit Reader for document processing, as it allows attackers to execute arbitrary code with the privileges of the currently running process. The attack surface is broad since PDF documents are commonly shared through email, web downloads, and file transfers, making this vulnerability particularly dangerous in enterprise environments. The exploitation process typically involves crafting a malicious PDF file containing specially formatted field elements that trigger the type confusion during parsing, followed by the execution of malicious code that leverages the corrupted memory state to gain control over the application's execution flow. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1203 for Exploitation for Client Execution and T1059 for Command and Scripting Interpreter, demonstrating how the flaw can be weaponized to achieve persistent access or further system compromise.
Organizations should prioritize immediate remediation by updating to Foxit Reader version 9.0.1 or later, which includes patches addressing the type confusion vulnerability. System administrators should implement network-level controls to block access to suspicious PDF content and consider deploying application whitelisting policies to restrict execution of untrusted PDF files. Additional mitigations include disabling JavaScript execution within Foxit Reader, implementing sandboxing techniques, and conducting regular security assessments to identify potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper input validation and memory management in client-side applications, particularly those handling untrusted data formats like PDF documents. Security teams should also monitor for indicators of compromise related to this vulnerability and ensure that all endpoints are regularly updated to maintain protection against similar threats that may arise from similar parsing vulnerabilities in other PDF processing libraries.