CVE-2017-5886 in PoDoFo
Summary
by MITRE
Heap-based buffer overflow in the PoDoFo::PdfTokenizer::GetNextToken function in PdfTokenizer.cpp in PoDoFo 0.9.4 allows remote attackers to have unspecified impact via a crafted file.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/03/2020
The heap-based buffer overflow vulnerability identified as CVE-2017-5886 resides within the PoDoFo document processing library version 0.9.4, specifically within the PdfTokenizer::GetNextToken function located in PdfTokenizer.cpp. This flaw represents a critical security weakness that can be exploited by remote attackers through the careful crafting of malicious PDF files. The vulnerability stems from inadequate input validation and memory management practices during the tokenization process of PDF documents, where the application fails to properly bounds-check data when processing certain token sequences. The heap-based nature of this overflow indicates that the vulnerable code manipulates heap-allocated memory regions without proper size verification, creating opportunities for attackers to overwrite adjacent memory locations and potentially execute arbitrary code.
The technical exploitation of this vulnerability occurs when PoDoFo processes a specially crafted PDF file that contains malformed token structures designed to trigger the buffer overflow condition. During normal operation, the PdfTokenizer::GetNextToken function expects well-formed PDF token sequences and allocates memory buffers accordingly. However, when confronted with malicious input, the function fails to validate the size of incoming data against allocated buffer boundaries, allowing attackers to write beyond the intended memory limits. This condition can lead to memory corruption that may result in application crashes, denial of service conditions, or more severe outcomes including arbitrary code execution depending on the specific memory layout and exploitation techniques employed. The unspecified impact mentioned in the CVE description reflects the potential severity variations that could occur based on system configurations and exploitation methods.
The operational impact of CVE-2017-5886 extends beyond simple application instability, as it represents a significant threat to systems that rely on PoDoFo for PDF processing tasks. Organizations using this library in web applications, document management systems, or any environment where untrusted PDF files are processed face substantial risk of compromise. The vulnerability's remote exploitability means that attackers can trigger the condition without requiring local access to the target system, making it particularly dangerous in web-facing applications. From a cybersecurity perspective, this vulnerability aligns with CWE-121 heap-based buffer overflow classification and can be mapped to ATT&CK techniques involving code injection and privilege escalation through memory corruption. The vulnerability demonstrates poor defensive programming practices and highlights the importance of robust input validation and memory safety mechanisms in document processing libraries.
Mitigation strategies for CVE-2017-5886 should prioritize immediate remediation through the deployment of PoDoFo version 0.9.5 or later, which contains the necessary patches to address the buffer overflow condition. Organizations should implement comprehensive input sanitization measures for all PDF processing workflows, including validation of document structure and content before processing. Network-level defenses such as web application firewalls and content filtering systems can provide additional protection by identifying and blocking suspicious PDF file patterns. Security teams should also conduct thorough code reviews and penetration testing of applications that utilize PoDoFo to identify potential similar vulnerabilities in custom implementations. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date third-party libraries and implementing proper memory safety practices in document processing applications, particularly those handling untrusted input data.