CVE-2020-18971 in PoDoFo
Summary
by MITRE • 08/25/2021
Stack-based Buffer Overflow in PoDoFo v0.9.6 allows attackers to cause a denial of service via the component 'src/base/PdfDictionary.cpp:65'.
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Analysis
by VulDB Data Team • 01/20/2025
The vulnerability CVE-2020-18971 represents a stack-based buffer overflow in the PoDoFo library version 0.9.6, specifically within the PdfDictionary.cpp component at line 65. This critical flaw exists in the handling of PDF dictionary objects and demonstrates a classic software security weakness that can be exploited to disrupt application functionality. The PoDoFo library serves as a comprehensive PDF processing toolkit used by numerous applications for creating, modifying, and parsing PDF documents, making this vulnerability particularly concerning for software systems that rely on robust PDF handling capabilities.
The technical implementation of this buffer overflow occurs when the application processes malformed PDF dictionary objects that exceed expected memory boundaries during stack allocation. The flaw manifests in the PdfDictionary.cpp file where insufficient bounds checking allows an attacker to provide input data that overflows the allocated stack buffer, potentially leading to memory corruption. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is categorized as a fundamental memory safety issue where data written to a buffer exceeds the buffer's allocated size. The specific location at line 65 indicates a failure in input validation during dictionary processing operations, where the application does not adequately verify the size or structure of incoming PDF dictionary elements before attempting to store them in stack memory.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the application context. When exploited, the buffer overflow can cause application crashes, leading to denial of service conditions that prevent legitimate users from accessing PDF processing functionality. However, the vulnerability's potential for exploitation increases when considering that many applications using PoDoFo may not implement proper error handling or input sanitization around PDF parsing operations. Attackers could craft malicious PDF files containing oversized dictionary entries that trigger the overflow, causing the target application to terminate unexpectedly. The vulnerability affects systems where PoDoFo is integrated into document processing pipelines, content management systems, or any software that handles PDF document manipulation, potentially creating widespread service disruption across multiple applications.
Mitigation strategies for CVE-2020-18971 should prioritize immediate remediation through software updates to PoDoFo version 0.9.7 or later, which contains the necessary patches for the buffer overflow vulnerability. Organizations should implement comprehensive input validation measures that include bounds checking for all PDF dictionary elements, particularly when processing untrusted documents. The implementation of address space layout randomization and stack canaries can provide additional protection layers against exploitation attempts, though these are considered defensive measures rather than primary fixes. Security teams should conduct thorough vulnerability assessments of all applications utilizing PoDoFo to identify potential attack surfaces and implement proper error handling procedures that prevent crash conditions from occurring during PDF processing operations. Additionally, network segmentation and application whitelisting can help limit the impact of potential exploitation by restricting access to vulnerable applications and implementing monitoring for suspicious PDF processing activities that might indicate exploitation attempts.