CVE-2018-17635 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 desc 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-6471.
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Analysis
by VulDB Data Team • 05/05/2020
CVE-2018-17635 represents a critical remote code execution vulnerability affecting Foxit Reader version 9.2.0.9297, classified under CWE-476 as Null Pointer Dereference, which falls within the broader category of improper error handling in software applications. This vulnerability resides in the PDF processing engine's handling of the desc property within PDF objects, where the application fails to validate whether an object exists before attempting to perform operations on it. The flaw manifests when Foxit Reader processes maliciously crafted PDF files that contain specially constructed desc properties that trigger the null pointer dereference condition, ultimately leading to arbitrary code execution within the context of the current process.
The exploitation of this vulnerability requires user interaction through either visiting a malicious webpage that hosts a specially crafted PDF file or opening a malicious PDF document directly, making it a prime candidate for drive-by download attacks and social engineering campaigns. This attack vector aligns with ATT&CK technique T1203 - Exploitation for Client Execution, which specifically targets vulnerabilities in applications that process user-supplied content. The vulnerability's impact extends beyond simple code execution as it allows attackers to operate within the privileges of the Foxit Reader process, potentially enabling further escalation attacks or data exfiltration activities.
The technical root cause of this vulnerability stems from inadequate input validation and memory management practices within the PDF parser component of Foxit Reader. When the application encounters a PDF object with an invalid or malformed desc property, it proceeds to dereference a null pointer without proper validation checks, leading to a crash that can be leveraged to inject and execute malicious code. This type of vulnerability is particularly dangerous because it operates at the application level without requiring elevated privileges, and the exploitation can occur through standard web browsing activities, making it difficult to detect and prevent through traditional network-based security measures.
Organizations and users must implement immediate mitigations including updating to Foxit Reader version 9.2.1 or later, which contains the necessary patches to address this vulnerability. Additionally, administrators should consider implementing web filtering solutions that can block access to known malicious PDF hosting sites and employ sandboxing techniques for PDF processing. The vulnerability also highlights the importance of Principle of Least Privilege implementation, where Foxit Reader should be configured to run with minimal required permissions. Security monitoring should focus on detecting unusual PDF processing activities and network connections initiated by the application, as these may indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of regular software updates and proper input validation in preventing remote code execution attacks, particularly in widely used applications like PDF readers that process untrusted content from the internet.