CVE-2018-17691 in PhantomPDF
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit PhantomPDF 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 conversion of HTML files to PDF. 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-7128.
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Analysis
by VulDB Data Team • 08/01/2024
CVE-2018-17691 represents a critical remote code execution vulnerability affecting Foxit PhantomPDF version 9.2.0.9297, demonstrating a classic null pointer dereference flaw that aligns with CWE-476. This vulnerability resides within the HTML to PDF conversion functionality, where the software fails to validate object existence before performing operations on it. The flaw constitutes a fundamental security oversight in input validation and memory management practices, creating a pathway for malicious actors to execute arbitrary code remotely. The vulnerability requires user interaction through visiting a malicious webpage or opening a crafted file, making it a prime example of a client-side exploitation vector that leverages social engineering techniques. Attackers can exploit this weakness by crafting specially designed HTML content that, when processed by the vulnerable PDF converter, triggers the null pointer dereference condition. This condition allows the execution of malicious code within the context of the current process, potentially enabling full system compromise. The vulnerability's impact extends beyond simple code execution, as it can be used to bypass security controls and escalate privileges within the target environment. The issue demonstrates poor defensive programming practices and highlights the importance of proper object validation and error handling in software development lifecycle. From an operational perspective, this vulnerability presents a significant risk to organizations relying on Foxit PhantomPDF for document processing, as it can be exploited through web-based attacks without requiring local system access. The attack surface is expanded by the fact that PDF viewers are commonly used for processing untrusted content from web browsers, email attachments, and file sharing platforms, making this vulnerability particularly dangerous in enterprise environments.
The technical exploitation of CVE-2018-17691 follows a well-established pattern that aligns with ATT&CK technique T1203, where adversaries leverage application vulnerabilities to execute malicious code. The vulnerability's root cause stems from inadequate input sanitization and object validation mechanisms, which are fundamental requirements for secure software development. When the HTML to PDF conversion engine processes malformed input, it fails to check whether referenced objects exist before attempting operations on them, creating a predictable crash condition that can be manipulated for code execution. This flaw represents a classic buffer over-read or null pointer dereference scenario that can be exploited through controlled input manipulation. The vulnerability's exploitation requires careful crafting of HTML content that triggers the specific code path leading to the object validation failure, making it a targeted attack vector rather than a broad sweep vulnerability. Security researchers have noted that similar vulnerabilities in PDF processing engines have been exploited in the wild, particularly in targeted attacks against high-value targets in government and corporate sectors. The vulnerability's classification as a remote code execution flaw means that attackers can compromise systems without requiring physical access or local credentials, significantly expanding the potential attack surface.
Organizations affected by CVE-2018-17691 must implement immediate mitigation strategies to protect their systems from exploitation attempts. The most effective immediate solution involves applying the vendor-provided security patches and updates, which address the core object validation issue in the HTML to PDF conversion module. System administrators should also consider implementing network-based controls such as web application firewalls and content filtering solutions that can detect and block malicious HTML content targeting this specific vulnerability. Additional protective measures include disabling the HTML to PDF conversion functionality when not required, implementing strict file access controls, and conducting regular security assessments of PDF processing workflows. The vulnerability's impact on enterprise security operations requires comprehensive monitoring for suspicious PDF processing activities and anomalous network traffic patterns that might indicate exploitation attempts. Organizations should also consider implementing zero-trust security models that verify all content processing regardless of source, particularly for documents originating from untrusted sources. From a compliance perspective, this vulnerability demonstrates the critical importance of maintaining up-to-date security patches and following secure coding practices that prevent null pointer dereference conditions in enterprise software applications. The vulnerability serves as a reminder of the ongoing need for security awareness training, as user interaction requirements make social engineering attacks particularly effective against this type of client-side vulnerability. Regular security audits and penetration testing should include assessment of document processing applications to identify similar validation flaws that could be exploited in similar ways.