CVE-2016-1686 in Chrome
Summary
by MITRE
The CPDF_DIBSource::CreateDecoder function in core/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp in PDFium, as used in Google Chrome before 51.0.2704.63, mishandles decoder-initialization failure, which allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted PDF document.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-1686 resides within the PDFium library's CPDF_DIBSource::CreateDecoder function, specifically in the core/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp file. This flaw manifests in Google Chrome versions prior to 51.0.2704.63, creating a critical security gap that enables remote attackers to exploit a denial of service condition through carefully crafted PDF documents. The vulnerability operates at the intersection of document parsing and image rendering components within the PDF processing pipeline, where improper error handling during decoder initialization leads to unpredictable memory access patterns.
The technical mechanism behind this vulnerability involves a failure to properly validate or handle decoder initialization errors within the PDF rendering context. When PDFium attempts to process image data within PDF documents, the CreateDecoder function is responsible for setting up the appropriate decoding mechanism for various image formats. However, when this initialization process fails, the function does not adequately check for error conditions or properly terminate the operation, instead allowing execution to continue with uninitialized or improperly configured decoder states. This leads to an out-of-bounds read condition where the application attempts to access memory locations beyond the allocated buffer boundaries, potentially causing application crashes or system instability.
From an operational perspective, this vulnerability presents a significant risk to end users who may encounter malicious PDF documents through various attack vectors including email attachments, web downloads, or compromised websites. The remote exploitation capability means that attackers can craft PDF documents that, when opened in vulnerable Chrome versions, will trigger the out-of-bounds read condition and cause denial of service. This type of vulnerability can be particularly dangerous in enterprise environments where users may inadvertently open malicious documents, leading to service disruption or potential system compromise. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and represents a classic example of improper error handling in memory management operations.
The impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attack vectors. While the immediate effect is a crash or hang of the PDF rendering process, the underlying memory access issue could provide attackers with opportunities to gather information about memory layout or potentially execute code if combined with other vulnerabilities. The ATT&CK framework categorizes this type of vulnerability under initial access and execution techniques, as it represents a method for gaining a foothold through malicious document delivery. Security professionals should note that this vulnerability demonstrates the critical importance of proper error handling in security-sensitive code paths, particularly those involving untrusted input processing.
Mitigation strategies for CVE-2016-1686 primarily involve updating to patched versions of Google Chrome, specifically version 51.0.2704.63 or later, where the decoder initialization error handling has been corrected. Organizations should implement comprehensive patch management procedures to ensure timely deployment of security updates across all affected systems. Additional protective measures include implementing PDF content filtering, using sandboxing technologies, and deploying network-based security solutions that can detect and block malicious PDF documents. The vulnerability highlights the necessity of robust input validation and error handling practices in PDF processing libraries, emphasizing that even seemingly benign operations like image decoding can become security-critical when proper error boundaries are not maintained. Security teams should also consider implementing user education programs to reduce the risk of accidental exposure to malicious PDF content through social engineering attacks.