CVE-2018-20248 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 table pointers or invalid xref table data using the LoadFromFile, LoadFromString, LoadFromStream, 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-2018-20248 affects Foxit Quick PDF Library versions prior to 16.12, representing a critical memory safety issue that can lead to arbitrary code execution. This flaw manifests when the library processes malformed PDF files through several key functions including LoadFromFile, LoadFromString, LoadFromStream, DAOpenFile, and DAOpenFileReadOnly. The root cause lies in insufficient validation of xref table structures within PDF documents, specifically when encountering invalid xref table pointers or corrupted xref table data. These functions fail to properly sanitize input data before attempting to parse and process the PDF structure, creating a pathway for attackers to exploit memory access violations.
The technical implementation of this vulnerability stems from improper bounds checking during PDF parsing operations. When the library encounters malformed xref tables, it attempts to access memory locations beyond the allocated buffer boundaries, resulting in access violations that can crash the application or potentially be exploited for code execution. This type of out-of-bounds memory access represents a classic buffer overflow condition that aligns with CWE-125, which describes out-of-bounds read vulnerabilities, and CWE-787, which covers out-of-bounds write conditions. The vulnerability operates at the intersection of memory corruption and input validation failures, where the PDF parser does not adequately verify the integrity of the xref table structure before attempting to traverse it.
From an operational perspective, this vulnerability presents significant risks to organizations relying on Foxit Quick PDF Library for document processing and PDF manipulation. Attackers can craft malicious PDF files that trigger the access violation when opened by applications using the vulnerable library, potentially leading to denial of service conditions or remote code execution. The impact extends beyond simple application crashes as the vulnerability could be leveraged in targeted attacks against systems processing PDF documents, particularly in environments where automated PDF handling is common such as email servers, document management systems, or web applications. The exploitability of this vulnerability is enhanced by the fact that it can be triggered through multiple input methods, increasing the attack surface for potential exploitation.
Organizations should immediately upgrade to Foxit Quick PDF Library version 16.12 or later to mitigate this vulnerability, as this release includes proper bounds checking and input validation for xref table parsing operations. Additional mitigations include implementing strict PDF file validation processes, deploying sandboxing techniques for PDF processing, and monitoring for anomalous PDF handling behaviors that might indicate exploitation attempts. Security teams should also consider implementing network-based intrusion detection systems that can identify suspicious PDF file patterns and application behavior that might indicate exploitation of this vulnerability. The remediation approach should align with defensive programming principles and follow industry standards such as those outlined in the OWASP Top Ten and MITRE ATT&CK framework, particularly focusing on preventing code execution through memory corruption vulnerabilities and ensuring proper input validation across all file processing functions.