CVE-2016-8876 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 TIFF image embedded in the XFA stream in a PDF document, aka "Read Access Violation starting at FoxitReader."
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Analysis
by VulDB Data Team • 05/21/2019
The vulnerability identified as CVE-2016-8876 represents a critical out-of-bounds read flaw affecting Foxit Reader and PhantomPDF versions prior to 8.1 on Windows operating systems. This vulnerability manifests when the gflags application is enabled, creating a dangerous condition that allows remote attackers to execute arbitrary code through maliciously crafted TIFF images embedded within the XFA stream of PDF documents. The issue stems from insufficient input validation and memory management practices within the PDF rendering engine of these applications, specifically when processing embedded image data structures.
The technical exploitation of this vulnerability occurs through a carefully constructed TIFF image that is embedded within the XFA (XML Forms Architecture) stream of a PDF document. When the vulnerable software processes this malformed image data, it fails to properly validate the boundaries of memory access operations, leading to an out-of-bounds read condition. This condition allows attackers to access memory locations beyond the intended data boundaries, potentially enabling them to read sensitive information or manipulate program execution flow. The gflags application, which is used for debugging and system diagnostics, when enabled, exacerbates this vulnerability by altering memory protection mechanisms and making the system more susceptible to memory corruption attacks.
The operational impact of this vulnerability is severe as it provides remote attackers with a means to achieve arbitrary code execution without requiring local system access or user interaction beyond opening a malicious PDF document. This represents a significant escalation from traditional web-based attacks, as the vulnerability can be exploited through standard web browsing activities or email attachments containing malicious PDFs. The attack surface is particularly concerning given the widespread use of Foxit Reader and PhantomPDF in enterprise environments, where these applications are frequently used to process sensitive documents from external sources.
This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and demonstrates characteristics consistent with the attack patterns documented in the MITRE ATT&CK framework under techniques such as T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter). The flaw represents a classic buffer overflow vulnerability variant that exploits memory access violations in document processing libraries. Organizations should prioritize immediate patching of affected systems and consider implementing network segmentation controls to limit the potential impact of such attacks. Additionally, security monitoring should be enhanced to detect unusual memory access patterns or gflags-related system modifications that might indicate exploitation attempts. The vulnerability underscores the importance of robust input validation and memory safety practices in document processing software, particularly when handling complex data structures like embedded image formats within structured documents.