CVE-2016-6168 in Foxit Reader
Summary
by MITRE
Use-after-free vulnerability in Foxit Reader and PhantomPDF 7.3.4.311 and earlier on Windows allows remote attackers to cause a denial of service (application crash) and execute arbitrary code via a crafted PDF file.
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Analysis
by VulDB Data Team • 01/02/2020
The CVE-2016-6168 vulnerability represents a critical use-after-free flaw affecting Foxit Reader and PhantomPDF versions 7.3.4.311 and earlier on Windows platforms. This vulnerability resides in the PDF parsing functionality of these applications, specifically within how they handle memory management during document processing. The flaw manifests when the software attempts to access memory that has already been freed, creating a scenario where malicious actors can manipulate the application's memory state to execute arbitrary code or cause system instability. The vulnerability is particularly dangerous because it can be triggered remotely through the simple act of opening a maliciously crafted PDF file, eliminating the need for user interaction beyond the initial document opening. This makes it an ideal candidate for drive-by download attacks and remote exploitation campaigns.
The technical exploitation of this vulnerability follows a classic use-after-free pattern where an attacker crafts a PDF file containing specially designed objects that trigger improper memory handling within the vulnerable applications. When the PDF parser processes these malformed objects, it frees certain memory regions while still maintaining references to them, allowing subsequent operations to access this freed memory. This memory access violation can be leveraged to overwrite critical memory locations, redirect execution flow, and ultimately achieve arbitrary code execution. The vulnerability's impact extends beyond simple code execution to include potential denial of service conditions, where the application crashes and becomes unavailable to legitimate users. The flaw demonstrates poor memory management practices and inadequate input validation within the PDF processing pipeline, creating a persistent security risk for organizations relying on these document readers.
From an operational perspective, this vulnerability presents significant risks to enterprise environments where Foxit Reader and PhantomPDF are commonly deployed for document viewing and processing. The remote exploit capability means that attackers can compromise systems without requiring physical access or complex social engineering tactics. Security teams must consider the widespread adoption of these applications in corporate networks, educational institutions, and government agencies, where the potential for mass exploitation exists. The vulnerability can be exploited through various attack vectors including email attachments, web downloads, and malicious websites, making it particularly challenging to defend against. Organizations may face immediate operational disruptions when systems are compromised, leading to potential data loss, system downtime, and increased forensic investigation requirements.
Mitigation strategies for CVE-2016-6168 should prioritize immediate patch deployment from Foxit Corporation, as the vendor released updates addressing this specific vulnerability. Organizations should implement network-based controls such as PDF file filtering at perimeter defenses, blocking suspicious PDF content from entering the network. Application whitelisting and sandboxing techniques can provide additional layers of protection by restricting the execution environment of PDF viewers. Regular security assessments and vulnerability scanning should include checks for outdated Foxit Reader installations, with automated patch management systems ensuring timely updates. The vulnerability aligns with CWE-416, which describes the use of freed memory conditions, and maps to several ATT&CK techniques including T1203 for Exploitation for Client Execution and T1059 for Command and Scripting Interpreter. Organizations should also consider implementing endpoint detection and response solutions to monitor for suspicious memory access patterns and potential exploitation attempts, as traditional signature-based detection may not be sufficient to identify all variants of this exploit.