CVE-2016-8879 in Foxit
Summary
by MITRE
The thumbnail shell extension plugin (FoxitThumbnailHndlr_x86.dll) in Foxit Reader and PhantomPDF before 8.1 on Windows allows remote attackers to cause a denial of service (out-of-bounds write and application crash) via a crafted JPEG2000 image embedded in a PDF document, aka an "Exploitable - Heap Corruption" issue.
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Analysis
by VulDB Data Team • 05/21/2019
The vulnerability identified as CVE-2016-8879 represents a critical heap corruption issue within the thumbnail shell extension plugin of Foxit Reader and PhantomPDF versions prior to 8.1 on Windows platforms. This flaw manifests through the FoxitThumbnailHndlr_x86.dll component which handles thumbnail generation for PDF documents, creating a pathway for remote attackers to exploit the software through maliciously crafted JPEG2000 image files embedded within PDF documents. The vulnerability classifies under CWE-787, which specifically addresses out-of-bounds writes in heap memory, making it a prime example of heap-based buffer overflow conditions that can lead to arbitrary code execution or system instability. The issue is particularly concerning because it operates at the shell extension level, allowing attackers to leverage the thumbnail generation feature to trigger memory corruption during normal document preview operations.
The technical exploitation of this vulnerability occurs when a user opens a PDF document containing a specially crafted JPEG2000 image that has been designed to trigger an out-of-bounds write condition within the FoxitThumbnailHndlr_x86.dll plugin. This occurs during the automatic thumbnail generation process that happens when users browse through PDF files or when the system attempts to display document previews in file explorers or other applications that utilize the shell extension. The out-of-bounds write corrupts heap memory structures, leading to application crashes or potentially more severe consequences including privilege escalation. This vulnerability maps directly to ATT&CK technique T1059 where adversaries use malicious code execution through legitimate system processes, and T1203 which involves the exploitation of software flaws to gain system access.
The operational impact of this vulnerability extends beyond simple denial of service conditions as it creates a persistent threat vector that can be exploited by attackers to disrupt normal business operations, particularly in environments where PDF documents are frequently shared or processed. Organizations using affected versions of Foxit Reader or PhantomPDF face significant risk of system instability and potential data exposure, especially when users interact with untrusted PDF documents. The vulnerability affects the core functionality of document preview systems, making it particularly dangerous in enterprise environments where users may encounter malicious documents through email attachments, web downloads, or shared network resources. This flaw undermines the security posture of organizations by creating an attack surface that can be exploited without user interaction beyond opening the malicious document, making it a high-priority issue for security teams to address through immediate patching or alternative security controls.
The recommended mitigation strategy involves immediate deployment of the patched versions of Foxit Reader and PhantomPDF 8.1 or later, which contain fixes for the heap corruption issue in the thumbnail shell extension. Organizations should also implement additional security measures including email filtering, web proxy configuration, and user education about the risks of opening untrusted PDF documents. Network segmentation and application whitelisting can help reduce the attack surface, while monitoring systems should be configured to detect unusual memory access patterns or application crashes that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory management in shell extensions, as these components often run with elevated privileges and have direct access to system resources, making them attractive targets for attackers seeking to escalate privileges or gain persistent access to systems.