CVE-2019-5047 in NitroPDF
Summary
by MITRE
An exploitable Use After Free vulnerability exists in the CharProcs parsing functionality of NitroPDF. A specially crafted PDF can cause a type confusion, resulting in a Use After Free. 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-2019-5047 represents a critical security flaw within NitroPDF's CharProcs parsing component that exposes users to potential remote code execution risks. This issue manifests as a use after free vulnerability, a class of memory corruption flaws that occur when a program continues to reference memory after it has been freed, creating opportunities for attackers to manipulate program execution flow. The vulnerability specifically impacts the parsing functionality that handles character processing within PDF documents, making it particularly dangerous given that PDF files are commonly encountered in enterprise environments and personal computing scenarios. The flaw enables attackers to craft malicious PDF documents that, when processed by NitroPDF, can trigger the vulnerable code path and potentially lead to arbitrary code execution.
The technical exploitation of this vulnerability involves a type confusion error that occurs during the parsing of CharProcs data structures within PDF files. This type confusion typically arises when the application fails to properly validate or distinguish between different data types during memory operations, allowing attackers to manipulate memory layout and object references. According to CWE classification, this vulnerability maps to CWE-415 which describes "Double Free" conditions, and CWE-476 which covers "NULL Pointer Dereference" scenarios that often accompany use after free conditions. The vulnerability demonstrates characteristics consistent with the ATT&CK framework's technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1203 for "Exploitation for Client Execution" as attackers can leverage such memory corruption flaws to execute malicious payloads through compromised applications.
The operational impact of CVE-2019-5047 extends beyond simple memory corruption, as it provides attackers with a potential pathway for privilege escalation and persistent access within affected systems. When a user opens a maliciously crafted PDF file, the vulnerability can be triggered during normal document processing operations, making exploitation particularly stealthy and difficult to detect through conventional security monitoring. The attack surface is significant given that NitroPDF is widely deployed in business environments where PDF processing is common, and the vulnerability affects multiple versions of the software, increasing the potential attack surface. Organizations utilizing NitroPDF for document management, electronic filing systems, and digital signature verification are particularly at risk, as these use cases often involve processing untrusted PDF content from external sources.
Mitigation strategies for this vulnerability require immediate software updates and patches from the vendor, as the flaw exists within core application functionality that cannot be easily bypassed through configuration changes. Security administrators should implement network-based protections such as PDF content filtering and sandboxing solutions to prevent potentially malicious documents from reaching end users. Additionally, user education regarding the risks of opening untrusted PDF files remains critical, though this approach is less effective against sophisticated targeted attacks. The vulnerability highlights the importance of regular security assessments and vulnerability management programs, as it demonstrates how seemingly benign functionality within document processing applications can contain critical security flaws. Organizations should also consider implementing application whitelisting policies that restrict execution of untrusted PDF processing software and maintain up-to-date threat intelligence feeds to identify potential exploitation attempts targeting this specific vulnerability.