CVE-2017-7378 in PoDoFo
Summary
by MITRE
The PoDoFo::PdfPainter::ExpandTabs function in PdfPainter.cpp in PoDoFo 0.9.5 allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) via a crafted PDF document.
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Analysis
by VulDB Data Team • 08/25/2020
The vulnerability identified as CVE-2017-7378 resides within the PoDoFo library version 0.9.5, specifically within the PdfPainter.cpp file in the PoDoFo::PdfPainter::ExpandTabs function. This flaw represents a heap-based buffer over-read condition that can be exploited by remote attackers through the manipulation of PDF documents. The issue manifests when the library processes specially crafted PDF content that triggers improper memory handling during tab expansion operations. The vulnerability is classified under CWE-125 as an out-of-bounds read, which occurs when the application attempts to read memory beyond the allocated buffer boundaries. This type of vulnerability falls within the broader category of memory safety issues that have been extensively documented in the software security community and aligns with ATT&CK technique T1059.007 for execution through scripting languages or libraries.
The technical exploitation of this vulnerability involves the manipulation of PDF documents to trigger the ExpandTabs function with malformed input data that causes the application to read beyond allocated memory regions. When processing PDF content containing specially crafted tab characters or formatting instructions, the PdfPainter component fails to properly validate the boundaries of memory allocations, leading to a buffer over-read condition. This over-read typically occurs when the application attempts to expand tab characters in text formatting operations without adequate bounds checking. The heap-based nature of the vulnerability indicates that the memory corruption happens within the heap allocation area rather than on the stack, making the exploitation more complex but still potentially lethal for the target application. The resulting behavior includes application crashes and denial of service conditions that can be reliably triggered by remote attackers through crafted PDF documents.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can potentially be leveraged to cause more severe consequences within applications that utilize PoDoFo for PDF processing. Systems that rely on PoDoFo for document rendering, manipulation, or validation become vulnerable to remote exploitation when handling untrusted PDF content. The vulnerability affects any application that integrates PoDoFo 0.9.5 or earlier versions, including document management systems, PDF viewers, and content processing applications. Attackers can construct malicious PDF files that, when opened or processed by vulnerable applications, will trigger the buffer over-read condition and cause the target application to crash. This creates a significant risk for organizations that process PDF documents from untrusted sources, as the vulnerability can be exploited without requiring any special privileges or user interaction beyond opening the malicious document.
Mitigation strategies for CVE-2017-7378 primarily focus on updating to patched versions of the PoDoFo library, with version 0.9.6 and later containing the necessary fixes for the buffer over-read condition. Organizations should prioritize patch management to ensure all systems utilizing PoDoFo are updated to versions that address this vulnerability. Additionally, implementing proper input validation and sanitization measures can provide defense-in-depth protection, particularly when processing untrusted PDF content. Security measures should include sandboxing PDF processing operations, implementing strict memory access controls, and deploying intrusion detection systems that can identify potential exploitation attempts. The vulnerability highlights the importance of proper bounds checking in memory management operations and underscores the need for comprehensive security testing of third-party libraries used in document processing applications. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, while maintaining regular security assessments to identify similar vulnerabilities in other components of their PDF processing pipelines.