CVE-2018-17706 in PhantomPDF
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit PhantomPDF Phantom PDF 9.1.5096. 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 fxhtml2pdf. The issue results from the lack of proper validation of user-supplied data, which can result in a memory access past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code under the context of the current process. Was ZDI-CAN-6230.
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Analysis
by VulDB Data Team • 04/07/2020
This vulnerability represents a critical buffer overflow flaw in Foxit PhantomPDF version 9.1.5096 that enables remote code execution through the fxhtml2pdf component. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data during HTML to PDF conversion processes. Attackers can exploit this weakness by crafting malicious HTML content that triggers memory corruption when processed by the vulnerable PDF rendering engine. The flaw specifically manifests as an out-of-bounds memory access condition that occurs when the application attempts to write data beyond the allocated buffer boundaries, creating potential for arbitrary code execution within the context of the running process.
The exploitation requires user interaction through visiting a malicious webpage or opening a specially crafted file, making this a remote code execution vulnerability with significant attack surface implications. This characteristic aligns with attack patterns described in the MITRE ATT&CK framework under the technique of "Exploitation for Client Execution" where adversaries leverage application vulnerabilities to execute malicious code on target systems. The vulnerability's classification as a buffer overflow directly corresponds to CWE-121, which describes heap-based buffer overflow conditions that occur when data is written beyond the bounds of a buffer allocated on the heap. The memory corruption vulnerability allows attackers to potentially overwrite critical memory regions including return addresses or function pointers, enabling full control over the application's execution flow.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise when attackers leverage additional attack vectors. Since the exploitation occurs within the context of the current process, successful exploitation can lead to privilege escalation depending on the permissions under which PhantomPDF operates. This vulnerability affects organizations that rely on PDF processing for document management, business operations, and electronic workflows where users may encounter malicious content through email attachments, web downloads, or document sharing platforms. The vulnerability's presence in a widely used PDF viewer application creates significant risk for enterprise environments where users frequently interact with untrusted document sources.
Organizations should implement immediate mitigation strategies including applying the vendor-provided security patches, implementing network segmentation to limit access to potentially malicious content, and deploying web application firewalls to filter suspicious HTML content. The vulnerability demonstrates the importance of input validation and proper memory management practices as outlined in the OWASP Top Ten security risks. Security teams should also consider implementing user education programs to reduce the likelihood of successful exploitation through social engineering attacks that rely on user interaction. Additionally, monitoring for suspicious PDF processing activities and implementing application whitelisting controls can provide additional defense layers against exploitation attempts. The vulnerability serves as a reminder of the critical need for regular security updates and comprehensive vulnerability management programs that address both known and emerging threats in document processing applications.