CVE-2018-8000 in PoDoFo
Summary
by MITRE
In PoDoFo 0.9.5, there exists a heap-based buffer overflow vulnerability in PoDoFo::PdfTokenizer::GetNextToken() in PdfTokenizer.cpp, a related issue to CVE-2017-5886. Remote attackers could leverage this vulnerability to cause a denial-of-service or potentially execute arbitrary code via a crafted pdf file.
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Analysis
by VulDB Data Team • 02/21/2023
The heap-based buffer overflow vulnerability identified as CVE-2018-8000 resides within the PoDoFo library version 0.9.5, specifically within the PdfTokenizer::GetNextToken() function located in PdfTokenizer.cpp. This flaw represents a critical security weakness that arises from inadequate input validation and memory management during PDF token processing operations. The vulnerability is particularly concerning as it demonstrates a direct path for remote code execution or denial-of-service attacks through manipulation of PDF files, making it a significant threat to systems that process untrusted PDF content. The issue is classified under CWE-121 as a stack-based buffer overflow, though the heap-based nature of this particular instance indicates more complex memory corruption patterns that can lead to unpredictable system behavior. The vulnerability stems from the library's inability to properly handle oversized or malformed data when parsing PDF tokens, creating opportunities for attackers to craft malicious PDF files that trigger memory corruption during parsing operations.
The technical exploitation of this vulnerability occurs when a malicious PDF file contains specially crafted data that exceeds the allocated buffer size during tokenization. The PdfTokenizer::GetNextToken() function fails to validate the length of incoming data segments before copying them into fixed-size buffers, allowing attackers to overwrite adjacent memory locations on the heap. This memory corruption can potentially overwrite function pointers, return addresses, or other critical program data structures, enabling remote attackers to redirect program execution flow or cause application crashes. The vulnerability's remote exploitation capability means that simply opening or processing a malicious PDF file can trigger the buffer overflow, making it particularly dangerous for web applications, email servers, and document processing systems that automatically parse PDF content. The issue is related to CVE-2017-5886, indicating a pattern of similar buffer overflow vulnerabilities within the PoDoFo library's tokenization components, suggesting systemic weaknesses in the library's input handling mechanisms.
The operational impact of CVE-2018-8000 extends beyond simple denial-of-service conditions to potentially enable complete system compromise. When exploited successfully, this vulnerability can allow attackers to execute arbitrary code with the privileges of the affected application, potentially leading to full system compromise. The heap-based nature of the overflow provides attackers with more sophisticated exploitation opportunities compared to stack-based variants, as heap corruption can be leveraged to manipulate heap metadata, create fake objects, or perform more complex attack vectors such as heap spraying or use-after-free conditions. Systems utilizing PoDoFo for PDF processing, including document management systems, web applications, and enterprise content management platforms, face significant risk exposure. The vulnerability affects any application that relies on PoDoFo for PDF parsing, particularly those that process untrusted or user-uploaded PDF files without proper sanitization or validation. Network-based attacks can be particularly effective as attackers can deliver malicious PDF content through various channels including email attachments, web downloads, or document sharing platforms.
Mitigation strategies for CVE-2018-8000 should focus on immediate patching and implementation of defensive programming practices. The most effective solution involves upgrading to a patched version of PoDoFo that addresses the buffer overflow in PdfTokenizer::GetNextToken() function, as provided by the vendor's security advisories. Organizations should implement strict input validation and sanitization procedures for all PDF processing workflows, including the use of sandboxed environments and restricted execution contexts when handling untrusted PDF content. Network-level defenses such as PDF content filtering and deep packet inspection can help detect and block malicious PDF files before they reach vulnerable applications. Additionally, implementing memory protection mechanisms like stack canaries, address space layout randomization, and data execution prevention can significantly reduce the exploitation success rate of heap-based buffer overflows. Security monitoring should include detection of unusual memory access patterns and process behavior that might indicate exploitation attempts. The vulnerability highlights the importance of following secure coding practices such as those recommended in the OWASP Secure Coding Practices and adheres to ATT&CK technique T1203 for legitimate program execution, where attackers leverage vulnerabilities in legitimate programs to execute malicious code. Organizations should also consider implementing automated vulnerability scanning and penetration testing to identify similar issues in other PDF processing libraries or components within their software ecosystem.