CVE-2016-4063 in Foxit
Summary
by MITRE
Use-after-free vulnerability in Foxit Reader and PhantomPDF before 7.3.4 on Windows allows remote attackers to execute arbitrary code via an object with a revision number of -1 in a PDF document.
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Analysis
by VulDB Data Team • 10/21/2018
The vulnerability identified as CVE-2016-4063 represents a critical use-after-free flaw affecting Foxit Reader and PhantomPDF versions prior to 7.3.4 on Windows operating systems. This vulnerability resides within the PDF parsing functionality of these document readers, specifically when processing malformed PDF objects with revision numbers set to -1. The flaw stems from improper memory management practices during the handling of PDF document structures, creating a scenario where freed memory locations can be accessed and potentially overwritten by malicious code. Such vulnerabilities are particularly dangerous because they can be exploited remotely through crafted PDF files delivered via email attachments, web downloads, or malicious websites, making them prime targets for zero-day exploitation campaigns.
The technical implementation of this vulnerability involves the PDF parser's failure to properly validate the revision number field within PDF objects before attempting to access or manipulate associated memory structures. When a PDF document contains an object with a revision number of -1, the parsing logic incorrectly handles the memory allocation and deallocation sequence, leading to a situation where memory previously freed for an object becomes available for reuse before the original object reference is properly invalidated. This creates a race condition where an attacker can craft a malicious PDF that triggers the use-after-free condition, potentially allowing arbitrary code execution with the privileges of the victim user. The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in memory management, and demonstrates how improper handling of object lifecycle management can lead to severe security consequences.
The operational impact of CVE-2016-4063 extends beyond simple code execution capabilities, as it provides attackers with a pathway to establish persistent access to target systems. Attackers can leverage this vulnerability to deploy malware, escalate privileges, or conduct further reconnaissance activities once initial access is achieved. The remote exploit nature of this vulnerability means that organizations are particularly at risk when employees interact with untrusted PDF content, as the attack can be initiated without any local system interaction from the user. This vulnerability directly maps to several ATT&CK techniques including initial access through malicious files and execution through legitimate system binaries, making it a valuable target for advanced persistent threat actors seeking to establish footholds within enterprise environments.
Organizations should prioritize immediate patching of affected Foxit Reader and PhantomPDF installations to address this vulnerability, as the window for exploitation remains open for systems running versions prior to 7.3.4. Additional mitigations include implementing strict PDF file validation policies, deploying sandboxing solutions for PDF processing, and configuring email security appliances to scan and block potentially malicious PDF attachments. Network segmentation and user access controls can help limit the potential impact of successful exploitation, while regular security awareness training should emphasize the dangers of opening untrusted PDF documents. Security monitoring should include detection of anomalous PDF processing activities and memory access patterns that may indicate exploitation attempts. The vulnerability underscores the importance of maintaining up-to-date software patches and implementing defense-in-depth strategies to protect against sophisticated remote code execution threats that target widely used software applications.