CVE-2018-20249 in Quick PDF Library
Summary
by MITRE
In Foxit Quick PDF Library (all versions prior to 16.12), issue where loading a malformed or malicious PDF containing invalid xref entries using the DAOpenFile or DAOpenFileReadOnly functions may result in an access violation caused by out of bounds memory access.
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Analysis
by VulDB Data Team • 04/24/2020
The vulnerability identified as CVE-2018-20249 represents a critical memory safety issue within Foxit Quick PDF Library versions prior to 16.12. This flaw manifests when the library processes malformed PDF files through the DAOpenFile or DAOpenFileReadOnly functions, creating a scenario where improper handling of xref entries leads to unauthorized memory access patterns. The issue stems from inadequate input validation and memory management within the PDF parsing component, specifically affecting how the library interprets cross-reference tables that are integral to PDF document structure.
The technical root cause of this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions where programs access memory locations beyond the intended buffer boundaries. When a maliciously crafted PDF file contains invalid xref entries, the Quick PDF Library fails to properly validate these references before attempting to access memory locations. This results in an access violation that can manifest as a program crash or potentially enable more sophisticated exploitation techniques. The vulnerability specifically impacts the library's ability to handle malformed cross-reference entries, which are used to track object locations within PDF files and maintain document integrity.
From an operational perspective, this vulnerability presents significant risks to organizations relying on Foxit Quick PDF Library for document processing. Attackers could exploit this weakness by crafting malicious PDF files designed to trigger the out-of-bounds memory access during file opening operations. The impact extends beyond simple application crashes, as the access violation could potentially be leveraged for code execution or information disclosure, depending on the execution environment and memory layout. This makes the vulnerability particularly dangerous in automated processing environments where PDF files are handled without user intervention, such as in document management systems, email filtering solutions, or web applications that process user-uploaded documents.
The exploitation of this vulnerability falls under ATT&CK technique T1203, which involves gaining access to execution environments through manipulation of input data. Security professionals should consider this issue as part of broader defensive strategies against PDF-based attacks, particularly in environments where PDF processing is automated or where user-supplied documents are processed without extensive validation. Organizations should implement immediate mitigations including updating to Foxit Quick PDF Library version 16.12 or later, which contains patches addressing the memory access violation. Additionally, implementing PDF validation mechanisms and sandboxing techniques can provide additional layers of protection against exploitation attempts targeting this vulnerability.
The broader implications of this vulnerability highlight the importance of robust input validation and memory safety practices in document processing libraries. Given that PDF files are commonly used in enterprise environments and are frequently processed automatically, vulnerabilities in PDF parsing libraries can have cascading effects across multiple systems and applications. The vulnerability demonstrates the critical need for thorough testing of edge cases in document format handling, particularly when dealing with malformed or intentionally crafted input data that could be used to exploit memory safety issues in third-party libraries.