CVE-2018-17673 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 subtype property of a Annotation object. 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-6820.
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Analysis
by VulDB Data Team • 05/05/2020
CVE-2018-17673 represents a critical remote code execution vulnerability affecting Foxit Reader version 9.2.0.9297, classified under CWE-476 as NULL Pointer Dereference. This vulnerability stems from insufficient input validation within the PDF annotation processing subsystem where the application fails to verify the existence of an object before attempting operations on it. The flaw specifically manifests when handling the subtype property of Annotation objects, creating a condition where a null pointer dereference occurs during the parsing of maliciously crafted PDF documents. The vulnerability requires user interaction to exploit, meaning attackers must convince victims to visit malicious web pages or open compromised PDF files, making this a classic client-side attack vector.
The technical implementation of this vulnerability exploits the absence of proper null pointer checks in the annotation object handling code. When Foxit Reader processes a PDF containing a malformed annotation with an invalid subtype property, the application attempts to access memory locations without first confirming that the referenced object exists. This primitive error creates a predictable execution flow that attackers can manipulate to achieve arbitrary code execution within the context of the current process. The vulnerability is particularly dangerous because it operates at the application level, bypassing many traditional network-based security controls and operating within the trusted environment of a legitimate PDF reader application.
From an operational perspective, this vulnerability presents significant risk to organizations relying on Foxit Reader for document processing, as it enables attackers to execute malicious payloads without requiring elevated privileges or complex attack chains. The exploitation process leverages the typical user behavior of opening PDF documents, making it particularly effective in phishing campaigns or compromised website scenarios. The attack surface extends beyond individual users to include enterprise environments where PDF processing is common, potentially allowing attackers to establish persistent access or escalate privileges through the execution of malicious code. This vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) within the MITRE ATT&CK framework.
Organizations should implement immediate mitigations including disabling PDF preview features in web browsers, implementing strict file type validation for PDF documents, and deploying network-based intrusion detection systems to monitor for exploitation attempts. The most effective long-term solution involves upgrading to patched versions of Foxit Reader, as the vulnerability was addressed through proper null pointer validation and input sanitization. Additional protective measures include user education regarding suspicious PDF files, implementing sandboxing technologies for PDF processing, and establishing strict access controls for PDF document handling. Security teams should also monitor for indicators of compromise such as unusual process execution patterns or network connections initiated by Foxit Reader during PDF processing, as these may signal exploitation attempts.