CVE-2018-21236 in Foxit
Summary
by MITRE
An issue was discovered in Foxit Reader before 2.4.4. It has a NULL pointer dereference.
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Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2018-21236 represents a critical NULL pointer dereference flaw within Foxit Reader version 2.4.3 and earlier. This issue arises from inadequate input validation and error handling mechanisms within the PDF processing engine of the software. The vulnerability stems from the application's failure to properly validate pointers before attempting to dereference them during PDF document parsing operations. When a specially crafted PDF file is processed by the affected version of Foxit Reader, the application attempts to access a NULL memory pointer, leading to an immediate crash of the application. This behavior manifests as an unhandled exception that terminates the application process, effectively creating a denial of service condition for end users who encounter such malicious documents. The flaw exists in the document parsing logic where the software does not perform proper null checks before accessing memory locations that may not have been properly initialized or allocated.
The technical exploitation of this vulnerability requires an attacker to craft a malicious PDF file that triggers the specific code path leading to the NULL pointer dereference. This typically involves creating PDF objects or structures that, when parsed by Foxit Reader, cause the application to attempt to access memory through an uninitialized or improperly allocated pointer. The vulnerability can be classified under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. From an operational perspective, this vulnerability presents a significant risk to organizations that rely on Foxit Reader for document processing, as it can be exploited through simple email attachments or web downloads containing malicious PDF content. The attack surface is broad since PDF files are commonly used across enterprise environments and can be easily distributed through various channels including email systems, web portals, and file sharing platforms.
The impact of this vulnerability extends beyond simple application crashes and can potentially enable more sophisticated attacks if the attacker can leverage the crash to execute arbitrary code or gain additional system access. While the immediate effect is a denial of service condition that prevents legitimate users from accessing PDF documents, the underlying flaw suggests potential weaknesses in the application's memory management and input validation processes. Security researchers have noted that NULL pointer dereference vulnerabilities often indicate broader architectural issues within software applications, particularly concerning proper error handling and memory allocation practices. The vulnerability can be mapped to ATT&CK technique T1203 which describes the use of application crashes or errors to disrupt system operations and potentially gain unauthorized access. Organizations utilizing Foxit Reader should consider implementing additional security controls such as PDF sandboxing, content filtering, and application whitelisting to mitigate the risk associated with this vulnerability. The recommended mitigation strategy includes immediate patching to version 2.4.4 or later, which contains the necessary fixes to properly validate pointers before dereferencing and implement robust error handling mechanisms. Additionally, security teams should conduct thorough vulnerability assessments to identify any other potential NULL pointer dereference conditions within similar PDF processing applications and ensure that proper input validation controls are in place throughout the software development lifecycle.