CVE-2018-21243 in PhantomPDF
Summary
by MITRE
An issue was discovered in Foxit PhantomPDF before 8.3.6. It has COM object mishandling when Microsoft Word is used.
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Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2018-21243 represents a critical com object mishandling issue within Foxit PhantomPDF software versions prior to 8.3.6. This flaw specifically manifests when the PDF reader interacts with Microsoft Word through component object model interfaces, creating a dangerous condition that can be exploited by malicious actors. The vulnerability stems from improper handling of COM objects during the integration process between these two Microsoft products, where Foxit PhantomPDF fails to correctly manage the object lifecycle and memory allocation when communicating with Word's COM components.
The technical nature of this vulnerability places it within the realm of software integration flaws and improper resource management, aligning with CWE-416 which addresses use after free conditions and CWE-787 which covers out-of-bounds writes. When Foxit PhantomPDF attempts to interact with Microsoft Word through COM interfaces, the application does not properly validate or manage the references to COM objects, leading to potential memory corruption or arbitrary code execution scenarios. This issue is particularly concerning because it leverages the trusted relationship between Microsoft Office applications and PDF readers, exploiting the inherent trust model that exists when these applications interact through standard COM protocols.
The operational impact of this vulnerability extends beyond simple exploitation as it creates a persistent security risk for organizations using affected versions of Foxit PhantomPDF. Attackers can potentially leverage this flaw to execute malicious code with the privileges of the user running the PDF reader, effectively bypassing many traditional security controls. The vulnerability can be triggered through malicious PDF files that contain specially crafted elements designed to force the reader into interacting with Word's COM interfaces, making it particularly dangerous in targeted attack scenarios or when users open untrusted documents. This creates a significant risk for enterprise environments where PDF documents are commonly shared and opened by employees with varying privilege levels.
Organizations should immediately implement mitigations including updating Foxit PhantomPDF to version 8.3.6 or later, which contains the necessary patches to address the COM object handling issues. System administrators should also consider implementing application whitelisting policies that restrict the execution of potentially malicious PDF files and monitor for unusual COM object interactions. Additionally, security teams should review their incident response procedures to ensure they can quickly identify and respond to potential exploitation attempts. The vulnerability highlights the importance of proper COM object lifecycle management in enterprise software and serves as a reminder of the risks associated with complex application integrations. Organizations should also consider implementing network-based protections such as intrusion detection systems that can identify suspicious COM object interactions and provide early warning of potential exploitation attempts.