CVE-2019-5053 in NitroPDF
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the Length parsing function of NitroPDF. A specially crafted PDF can cause a type confusion, resulting in a use-after-free condition. An attacker can craft a malicious PDF to trigger this vulnerability.
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Analysis
by VulDB Data Team • 01/07/2024
The vulnerability identified as CVE-2019-5053 represents a critical use-after-free condition within NitroPDF's Length parsing function, demonstrating a fundamental flaw in memory management and object lifecycle handling. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating opportunities for malicious exploitation. The flaw specifically manifests during the parsing of PDF documents, where NitroPDF fails to properly validate the structure and type of data being processed, leading to a scenario where memory corruption can occur through crafted input.
The technical implementation of this vulnerability involves a type confusion error that occurs when NitroPDF processes the Length field within PDF objects. When parsing a maliciously crafted PDF document, the application incorrectly handles the data type of the Length parameter, causing it to free memory associated with one object type while subsequently attempting to access it as another type. This fundamental mismatch between expected and actual data types creates a use-after-free condition that can be exploited by attackers to execute arbitrary code. The vulnerability is classified under CWE-416 as a use-after-free error, which is a well-documented weakness in software security that has been consistently identified in various PDF processing libraries and applications. The specific nature of this flaw indicates inadequate input validation and memory management practices within the PDF parsing engine.
The operational impact of CVE-2019-5053 extends beyond simple memory corruption, as it provides attackers with a potential pathway to achieve remote code execution within the context of the NitroPDF application. When successfully exploited, this vulnerability allows an attacker to craft a malicious PDF document that, when opened or processed by the vulnerable application, can trigger the use-after-free condition. The exploitation typically involves creating a PDF file with carefully constructed Length fields that cause the application to free memory containing object references while maintaining pointers to those freed locations. This scenario aligns with ATT&CK technique T1203, which describes the use of memory corruption vulnerabilities to execute malicious code. The vulnerability affects users who open PDF files with NitroPDF, making it particularly dangerous in environments where PDF documents are frequently shared and opened by multiple users.
Mitigation strategies for CVE-2019-5053 should focus on immediate patching and implementation of defensive measures. Organizations should prioritize updating to the latest version of NitroPDF that addresses this specific vulnerability, as vendors typically release patches that correct the memory management issues and implement proper input validation for Length fields. Additional defensive measures include implementing sandboxing techniques for PDF processing, deploying content filtering solutions that scan PDF documents for suspicious structures, and establishing user education programs to avoid opening untrusted PDF files. Network-based security controls such as web application firewalls and intrusion prevention systems can also help detect and block malicious PDF files before they reach end users. The vulnerability demonstrates the importance of proper memory management practices and input validation in security-critical applications, particularly those handling untrusted data formats like PDF documents. Organizations should also consider implementing principle of least privilege controls to limit the damage that could occur if exploitation were to succeed, ensuring that PDF processing applications run with minimal required privileges and access rights.