CVE-2020-19474 in PDF2JSON
Summary
by MITRE • 07/22/2021
An issue has been found in function Gfx::doShowText in PDF2JSON 0.70 that allows attackers to cause a Denial of Service due to an Use After Free .
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Analysis
by VulDB Data Team • 07/26/2021
The vulnerability identified as CVE-2020-19474 represents a critical use after free condition within the PDF2JSON 0.70 library's Gfx::doShowText function. This flaw occurs when the application processes PDF documents and attempts to convert them to JSON format, creating a scenario where memory that has already been freed is subsequently accessed or manipulated by the program. The issue stems from improper memory management practices during the text rendering process, specifically when handling graphical elements within PDF documents. When an attacker crafts a malicious PDF file containing specially constructed text elements, the vulnerable function fails to properly manage memory references, leading to unpredictable behavior and system instability.
The technical implementation of this vulnerability falls under CWE-416, which specifically addresses use after free conditions in software applications. This weakness occurs when a program continues to reference memory after it has been freed, creating opportunities for attackers to manipulate program flow or cause system crashes. The PDF2JSON library's Gfx::doShowText function appears to improperly handle memory allocation and deallocation sequences during text processing, particularly when encountering complex or malformed PDF text objects. The vulnerability manifests as a denial of service condition because the program crashes or becomes unresponsive when attempting to access freed memory locations, effectively preventing legitimate users from processing PDF documents through the affected software.
From an operational perspective, this vulnerability poses significant risks to organizations that rely on PDF2JSON for document processing workflows. Attackers can exploit this weakness by uploading malicious PDF files to systems that utilize the library, causing denial of service conditions that disrupt normal operations. The impact extends beyond simple service interruption as this vulnerability can be leveraged in broader attack campaigns, potentially serving as a precursor to more sophisticated exploits. The vulnerability affects any system that integrates PDF2JSON 0.70, including web applications, document management systems, and automated processing pipelines that convert PDF content to structured JSON data. Organizations using this library in production environments face potential operational downtime and increased risk of service disruption.
The mitigation strategy for CVE-2020-19474 requires immediate attention through software updates and patches provided by the maintainers of PDF2JSON. Organizations should prioritize upgrading to versions that address the memory management issues within the Gfx::doShowText function and implement proper input validation for PDF files processed through the library. Additional defensive measures include deploying sandboxed processing environments, implementing strict PDF file validation before processing, and monitoring for unusual processing patterns that might indicate exploitation attempts. Security teams should also consider implementing network-based intrusion detection systems to identify potential exploitation attempts targeting this specific vulnerability. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, while the memory corruption aspect aligns with T1059.007 for command and scripting interpreter usage in exploitation scenarios. Organizations must also consider the broader implications of using legacy libraries and establish more robust software supply chain security practices to prevent similar vulnerabilities in future deployments.