CVE-2018-9954 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 y 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-5529.
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Analysis
by VulDB Data Team • 02/06/2020
CVE-2018-9954 represents a critical remote code execution vulnerability affecting Foxit Reader version 9.0.1.1049 that demonstrates a classic improper input validation flaw within the XFA (XML Forms Architecture) processing subsystem. This vulnerability resides in the button element handling mechanism where the y attribute parameter fails to validate object existence before operations are performed on it, creating a dangerous condition that can be exploited through maliciously crafted PDF documents. The flaw specifically manifests when the application processes XFA button elements and attempts to manipulate the y coordinate attribute without verifying that the target object reference is valid, leading to potential memory corruption and arbitrary code execution.
The technical exploitation of this vulnerability requires user interaction through either visiting a malicious webpage that hosts a crafted PDF or opening a malicious file directly, which aligns with the ATT&CK technique T1203 (Exploitation for Client Execution) and follows the CWE-476 pattern of null pointer dereference. When an attacker crafts a PDF document containing malicious XFA button elements with malformed y attribute values, the vulnerable Foxit Reader application processes these elements and attempts to perform operations on what it believes to be a valid object reference. However, due to the lack of proper validation, the application may attempt to access memory locations that are either invalid or contain unexpected data, potentially leading to heap corruption, stack overflow conditions, or controlled memory access patterns that allow for code execution.
The operational impact of this vulnerability extends beyond simple remote code execution as it represents a privilege escalation vector that operates under the context of the currently running Foxit Reader process, which typically runs with the privileges of the logged-in user. This means that successful exploitation could result in unauthorized access to sensitive user data, system file manipulation, or even further lateral movement within a network environment if the compromised system has elevated permissions. The vulnerability's classification as a remote code execution flaw places it within the high-risk category of security issues that require immediate attention, particularly given that Foxit Reader is widely deployed across enterprise environments for document processing and viewing.
Mitigation strategies for CVE-2018-9954 should include immediate patching of all affected Foxit Reader installations to version 9.0.1.1050 or later, which contains the necessary fixes for the XFA button element validation. Organizations should also implement network-based protections such as PDF file scanning and filtering at network perimeters to prevent malicious documents from reaching end users. Additionally, user education regarding the dangers of opening untrusted PDF files and implementing application whitelisting policies can provide defense-in-depth measures. The vulnerability's characteristics align with the ATT&CK tactic T1059 (Command and Scripting Interpreter) and T1068 (Local Privilege Escalation) as exploitation typically involves command execution within the application context and potential privilege escalation. Security teams should also consider implementing monitoring for unusual PDF processing activities and memory access patterns that could indicate exploitation attempts, particularly focusing on heap-based memory corruption indicators that are common in such validation flaws.