CVE-2018-17640 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit Reader 9.2.0.9297. 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 the Form count property. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-6477.
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Analysis
by VulDB Data Team • 05/05/2020
CVE-2018-17640 represents a critical buffer overflow vulnerability in Foxit Reader version 9.2.0.9297 that enables remote code execution through improper object validation during form processing. This vulnerability falls under the CWE-476 category of NULL Pointer Dereference, where the application fails to validate whether an object exists before attempting operations on it. The flaw specifically manifests in the Form count property handling mechanism, where the software does not properly validate object existence prior to accessing memory locations associated with form elements. Attackers can exploit this by crafting malicious PDF documents containing malformed form data that triggers the vulnerable code path when the reader processes the document. The vulnerability requires user interaction to be successfully exploited, as victims must open the malicious file or visit a compromised webpage hosting the malicious content. This attack vector aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute code on target systems. The security implications extend beyond simple code execution, as the vulnerability operates within the context of the current process, potentially allowing attackers to escalate privileges or access sensitive system resources. The root cause stems from inadequate input validation and memory management practices within the PDF parsing engine, where the application assumes certain objects will always be present without proper existence checks. This vulnerability represents a classic example of how improper validation can lead to arbitrary code execution, as the lack of null pointer checks creates opportunities for attackers to manipulate memory layout and execute malicious payloads. The impact is particularly severe given that Foxit Reader is widely used for document viewing, making it an attractive target for adversaries seeking persistent access to corporate networks through document-based attacks.
The technical exploitation of this vulnerability requires a deep understanding of PDF file structures and the specific parsing mechanisms within Foxit Reader's form handling components. When the application encounters a malformed Form count property, it attempts to access memory locations without verifying that the associated object references are valid, leading to a potential buffer overflow condition. This flaw demonstrates poor defensive programming practices and highlights the importance of implementing robust input validation at multiple layers of the application stack. The vulnerability's classification as a remote code execution issue means that attackers can compromise systems without requiring physical access or local network presence, making it particularly dangerous in enterprise environments. Security researchers have noted that similar vulnerabilities in PDF readers often stem from the complex nature of PDF parsing, where multiple object types and cross-references must be properly validated. The exploitation process typically involves crafting a PDF file with specifically designed form elements that trigger the memory corruption when processed by the vulnerable reader. This vulnerability also illustrates the broader challenge of securing document processing applications, where the need to support complex file formats creates numerous potential attack surfaces. Organizations using Foxit Reader are particularly at risk since the application runs with the privileges of the current user, potentially allowing attackers to access local files or execute malicious commands with the user's permissions.
Organizations affected by CVE-2018-17640 should implement immediate mitigation strategies including patching the vulnerable software to the latest version that addresses the form handling validation issues. The recommended approach involves deploying security updates from Foxit Corporation as soon as they become available, while also implementing network-based protections such as web application firewalls and content filtering solutions to block malicious PDF files. Security teams should also consider implementing user education programs to raise awareness about the risks of opening untrusted PDF documents and the importance of verifying document sources before processing. Additional mitigations include restricting user privileges when opening PDF files, implementing sandboxing techniques for document processing, and monitoring for unusual PDF processing activities that might indicate exploitation attempts. The vulnerability's classification as a remote code execution flaw necessitates comprehensive network monitoring and intrusion detection system deployments to identify potential exploitation attempts. Organizations should also conduct regular vulnerability assessments to identify other potentially vulnerable applications and ensure that all software components receive timely security updates. The incident highlights the importance of maintaining up-to-date security patches and implementing layered security approaches that protect against multiple attack vectors. Furthermore, organizations should establish incident response procedures specifically designed to handle remote code execution vulnerabilities in document processing applications, ensuring rapid response capabilities when similar vulnerabilities are discovered in the future.