CVE-2019-6735 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on vulnerable installations of Foxit Reader. 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 processing of PDF files. 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 buffer. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the current process. Was ZDI-CAN-7355.
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Analysis
by VulDB Data Team • 08/04/2023
The vulnerability identified as CVE-2019-6735 represents a critical buffer overread flaw within Foxit Reader's PDF processing engine, classified under CWE-125 as improper validation of buffer bounds. This vulnerability specifically affects installations of Foxit Reader that process PDF files, creating a pathway for remote attackers to extract sensitive information from memory locations beyond the intended buffer boundaries. The flaw manifests during the parsing of PDF documents, where the application fails to properly validate user-supplied data before attempting to read from allocated memory regions. Attackers can exploit this weakness by crafting malicious PDF files or hosting malicious web pages that, when accessed by an unsuspecting user, trigger the vulnerable code path within the reader application.
The technical implementation of this vulnerability stems from inadequate input validation mechanisms within the PDF parser component of Foxit Reader. When processing malformed or specially crafted PDF content, the application does not perform sufficient boundary checks before accessing memory locations, leading to a read past the end of an allocated buffer. This behavior allows attackers to potentially read adjacent memory contents that may contain sensitive data such as stack canaries, heap metadata, or other confidential information. The vulnerability requires user interaction to be exploited, meaning that victims must either visit a malicious webpage containing a crafted PDF or open a malicious PDF file directly, making this an effective vector for social engineering attacks. The attack chain typically involves initial access through phishing emails or compromised websites followed by exploitation of this buffer overread condition to gather information that could be leveraged for more sophisticated attacks.
The operational impact of CVE-2019-6735 extends beyond simple information disclosure, as it provides attackers with valuable memory layout information that can be used to facilitate more advanced exploitation techniques. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation, as the leaked memory information can aid in bypassing security mechanisms like stack canaries or address space layout randomization. The read past the end of buffer condition creates a potential for information leakage that can reveal process memory structures, helping attackers understand the memory layout and potentially enabling them to craft more effective exploits. While the immediate impact may appear limited to information disclosure, the vulnerability creates a foundation for more sophisticated attacks by providing attackers with the memory layout information necessary for advanced exploitation techniques. Organizations using Foxit Reader are particularly at risk since the application is widely deployed in enterprise environments, making this vulnerability a significant concern for organizations that handle sensitive documents and data.
Mitigation strategies for CVE-2019-6735 should focus on both immediate remediation and long-term security enhancements. The primary recommendation involves applying the vendor-provided security patches that address the buffer overread condition in Foxit Reader's PDF processing engine. Organizations should also implement network-based protections such as web application firewalls and content filtering systems that can detect and block malicious PDF content before it reaches end users. Additional defensive measures include implementing strict access controls for PDF file handling, regularly updating and patching all PDF reader applications, and conducting security awareness training to help users identify potential phishing attempts that could deliver malicious PDF files. The vulnerability demonstrates the importance of proper input validation and memory safety practices in software development, aligning with security standards that emphasize the need for robust boundary checking and defensive programming techniques to prevent buffer overflow conditions that could lead to information disclosure or code execution vulnerabilities.