CVE-2019-14291 in Xpdf
Summary
by MITRE
An issue was discovered in Xpdf 4.01.01. There is an out of bounds read in the function GfxPatchMeshShading::parse at GfxState.cc for typeA==6 case 3.
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Analysis
by VulDB Data Team • 11/13/2023
The vulnerability identified as CVE-2019-14291 represents a critical out-of-bounds read flaw within the Xpdf 4.01.01 PDF rendering library. This issue manifests specifically within the GfxPatchMeshShading::parse function located in the GfxState.cc source file, where the software fails to properly validate input data during the parsing of patch mesh shading objects. The vulnerability occurs exclusively when processing typeA==6 cases with case 3 conditions, indicating a specific edge case in the PDF shading implementation that lacks proper boundary checking mechanisms.
This technical flaw constitutes a memory safety issue that falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions in software implementations. The vulnerability stems from inadequate input validation and boundary checking within the PDF rendering engine's shading parser, where the application attempts to access memory locations beyond the allocated buffer boundaries. When a maliciously crafted PDF document contains patch mesh shading data with typeA set to 6 and case 3 conditions, the parser executes code that reads memory past the intended data boundaries, potentially exposing sensitive information or causing application instability.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it creates potential attack vectors for remote code execution or information disclosure. When exploited, the out-of-bounds read could allow attackers to extract sensitive data from memory locations adjacent to the corrupted buffer, potentially revealing cryptographic keys, user credentials, or other confidential information. This vulnerability affects any system that relies on Xpdf for PDF processing, including web applications, document management systems, and security scanning tools that utilize this library for PDF analysis. The flaw's exploitation requires a crafted PDF document that triggers the specific typeA==6 case 3 parsing path, making it somewhat targeted but still dangerous due to the potential for remote exploitation in web-based environments.
Mitigation strategies for CVE-2019-14291 should prioritize immediate patching of the Xpdf library to version 4.01.02 or later, which contains the necessary fixes for the out-of-bounds read condition. Organizations should implement defensive programming practices including input validation, boundary checking, and memory safety mechanisms to prevent similar issues in custom PDF processing applications. The vulnerability demonstrates the importance of proper input sanitization and boundary validation in graphics rendering libraries, as highlighted by ATT&CK technique T1059.007 for application layer execution. Additional protective measures include deploying sandboxing mechanisms for PDF processing, implementing network segmentation for systems handling PDF documents, and conducting regular security assessments of PDF rendering components to identify and remediate similar vulnerabilities before they can be exploited in real-world scenarios.