CVE-2016-8878 in Foxit
Summary
by MITRE
Out-of-Bounds read vulnerability in Foxit Reader and PhantomPDF before 8.1 on Windows, when the gflags app is enabled, allows remote attackers to execute arbitrary code via a crafted BMP image embedded in the XFA stream in a PDF document, aka "Data from Faulting Address may be used as a return value starting at FOXITREADER."
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Analysis
by VulDB Data Team • 05/21/2019
The vulnerability identified as CVE-2016-8878 represents a critical out-of-bounds read flaw affecting Foxit Reader and PhantomPDF versions prior to 8.1 on Windows operating systems. This vulnerability specifically manifests when the gflags application is enabled, creating a dangerous condition that remote attackers can exploit to achieve arbitrary code execution. The attack vector involves a crafted BMP image that is embedded within the XFA stream of a PDF document, making this a sophisticated attack that leverages the complex structure of PDF files and their embedded content handling mechanisms. The vulnerability's classification as a memory corruption issue places it squarely within the domain of software security flaws that can lead to complete system compromise when successfully exploited.
The technical nature of this vulnerability stems from improper bounds checking during the processing of BMP image data within the XFA (XML Forms Architecture) stream of PDF documents. When Foxit Reader or PhantomPDF processes a maliciously crafted PDF containing an embedded BMP image, the application fails to properly validate the image data boundaries before accessing memory locations. This allows the application to read data from memory locations beyond the intended buffer boundaries, potentially accessing sensitive memory regions that could contain return addresses, function pointers, or other critical execution context information. The gflags application, which is used for debugging and system monitoring, creates an environment where this out-of-bounds read can be manipulated to influence the program's execution flow in a way that allows arbitrary code execution. This technique aligns with common exploit patterns described in the CWE (Common Weakness Enumeration) catalog under CWE-129, which addresses improper validation of array indices, and CWE-125, which covers out-of-bounds read conditions.
The operational impact of this vulnerability is severe, as it enables remote code execution without requiring user interaction beyond opening a malicious PDF document. Attackers can craft PDF files that appear legitimate but contain embedded malicious content, making this a particularly dangerous threat in phishing campaigns or targeted attacks. The vulnerability affects a widely used PDF reader application, meaning that successful exploitation could result in complete system compromise, data theft, or deployment of additional malware. The fact that this vulnerability requires the gflags application to be enabled creates a specific attack scenario that security professionals must consider when assessing system configurations, as it represents a privilege escalation path that may not be immediately obvious to administrators. This vulnerability demonstrates the importance of proper input validation and memory management in security-critical applications, particularly those that process untrusted data such as PDF documents.
Mitigation strategies for CVE-2016-8878 should focus on immediate patching of affected software versions, with Foxit Reader and PhantomPDF users upgrading to version 8.1 or later where the vulnerability has been addressed. System administrators should disable the gflags application on systems where it is not actively needed for debugging purposes, as this removes one of the prerequisites for successful exploitation. Network security measures including PDF content filtering and sandboxing of PDF processing can provide additional defense layers. The vulnerability also highlights the importance of maintaining up-to-date security patches and implementing proper application whitelisting policies to prevent execution of untrusted PDF content. From an ATT&CK framework perspective, this vulnerability maps to techniques involving execution through library loading and remote code execution, with potential lateral movement opportunities if exploited successfully. Organizations should implement comprehensive monitoring for suspicious PDF file processing activities and ensure that security updates are applied promptly across all systems that handle PDF documents. The vulnerability underscores the critical need for robust memory safety practices in software development and the importance of regular security assessments to identify and remediate similar flaws before they can be exploited in the wild.