CVE-2017-16573 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on vulnerable installations of Foxit Reader 8.3.1.21155. 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 LZWDecode filters. The issue results from the lack of proper validation of user-supplied data, which can result in a read past the end of an allocated object. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the current process. Was ZDI-CAN-5078.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/16/2019
CVE-2017-16573 represents a critical information disclosure vulnerability affecting Foxit Reader version 8.3.1.21155 that operates through remote code execution via malicious PDF files. This vulnerability resides within the LZWDecode filter parsing mechanism, where insufficient input validation permits attackers to manipulate memory access patterns. The flaw specifically enables a read past the end of allocated memory objects, creating potential for sensitive data exposure and system compromise. The vulnerability requires user interaction to exploit, meaning targets must either visit a malicious web page or open a crafted PDF file containing the malicious payload. This attack vector aligns with common social engineering tactics frequently employed in targeted attacks against enterprise environments. The technical implementation of this vulnerability demonstrates poor memory boundary checking during decompression operations, allowing attackers to traverse memory boundaries beyond intended data structures. The lack of proper bounds validation in the LZW decoding process creates opportunities for information leakage that could expose system memory contents, including potentially sensitive data, credentials, or application state information.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable full system compromise when combined with other exploitation techniques. Attackers can leverage the memory corruption aspects of this vulnerability to execute arbitrary code within the context of the Foxit Reader process, effectively gaining unauthorized access to the target system. This represents a significant escalation from initial exploitation to persistent system compromise, particularly in environments where Foxit Reader is frequently used for document processing. The vulnerability's classification under CWE-125 - "Out-of-bounds Read" demonstrates the fundamental nature of the memory safety issue, where the application fails to validate buffer boundaries during decompression operations. The attack surface is particularly concerning in enterprise environments where PDF document processing is common, as it can be triggered through email attachments, web downloads, or document sharing platforms. Security researchers have documented similar patterns in PDF processing libraries where decompression algorithms fail to properly validate input data, creating opportunities for attackers to manipulate memory access patterns. The vulnerability's exploitation complexity is moderate, requiring only user interaction through document opening rather than more sophisticated attack vectors.
Mitigation strategies for CVE-2017-16573 should prioritize immediate patching of affected Foxit Reader installations to address the LZWDecode filter parsing flaw. Organizations must implement comprehensive endpoint protection measures including PDF file scanning and sandboxing techniques to prevent execution of malicious documents. Network-based defenses should include web application firewalls and content filtering systems that can detect and block malicious PDF content. The vulnerability's exploitation requires user interaction, making user education and awareness programs critical components of defense strategies. Security teams should establish monitoring procedures to detect unusual PDF processing activities and implement strict access controls for document handling systems. Additionally, system hardening measures such as disabling unnecessary PDF features and implementing strict file type validation can reduce the attack surface. The vulnerability's characteristics align with ATT&CK technique T1204.002 - "User Execution: Malicious File" and T1059.007 - "Command and Scripting Interpreter: JavaScript" as attackers may leverage JavaScript within PDFs to trigger exploitation. Organizations should also consider implementing zero-trust network architectures that verify all file processing activities regardless of source or user identity, particularly for PDF documents that are commonly used in business communications. Regular vulnerability assessments and penetration testing focused on document processing applications can help identify similar memory safety issues in other software components. The remediation process should include comprehensive testing of patched versions to ensure that the fix does not introduce regressions in legitimate PDF processing functionality.