CVE-2018-3924 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Software's Foxit PDF Reader version 9.1.5096. A specially crafted PDF document can trigger a previously freed object in memory to be reused, resulting in arbitrary code execution. An attacker needs to trick the user into opening the malicious file to trigger this vulnerability. If the browser plugin extension is enabled, visiting a malicious site can also trigger the vulnerability.
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Analysis
by VulDB Data Team • 04/29/2023
The vulnerability identified as CVE-2018-3924 represents a critical use-after-free flaw within the JavaScript engine of Foxit PDF Reader version 9.1.5096. This type of vulnerability occurs when a program continues to reference memory locations that have already been freed, creating opportunities for attackers to manipulate memory contents and potentially execute arbitrary code. The issue stems from improper memory management practices within the PDF rendering engine that processes JavaScript commands embedded in PDF documents. Such vulnerabilities are particularly dangerous because they can be triggered through legitimate PDF document parsing operations, making them difficult to detect and prevent without comprehensive security measures.
The technical exploitation of this vulnerability involves crafting a malicious PDF document that contains specially constructed JavaScript code designed to trigger a use-after-free condition during normal PDF processing. When the vulnerable Foxit PDF Reader parses this document, it executes JavaScript commands that cause memory to be freed while references to that memory remain in the program's execution flow. Attackers can then manipulate the freed memory location to contain malicious code or data structures that will be executed when the program attempts to access the previously freed object. This particular flaw falls under CWE-416 which specifically addresses use-after-free conditions, making it a well-documented and dangerous class of memory corruption vulnerabilities that have been exploited in numerous high-profile attacks.
The operational impact of this vulnerability extends beyond simple document viewing, as it creates a potential attack vector through multiple delivery mechanisms. Users can be compromised simply by opening a malicious PDF file, which makes this vulnerability particularly dangerous in environments where users frequently open PDF documents from untrusted sources. Additionally, when the browser plugin extension is enabled, visiting a malicious website becomes a potential trigger point, expanding the attack surface significantly. This dual delivery mechanism increases the likelihood of successful exploitation and reduces the need for social engineering techniques beyond simply convincing users to visit compromised websites or open suspicious documents. The vulnerability demonstrates the inherent risks of complex software components that handle untrusted data, particularly in applications that must process rich media content with embedded scripting capabilities.
Organizations and individuals should implement multiple layers of defense to protect against exploitation of this vulnerability. Immediate remediation involves updating to the latest version of Foxit PDF Reader where the memory management issues have been addressed through proper memory deallocation and reference tracking mechanisms. System administrators should consider implementing application whitelisting policies that restrict execution of PDF readers from untrusted locations and deploy sandboxing solutions to isolate PDF processing operations. Network-based defenses such as web application firewalls and content filtering systems can help detect and block malicious PDF content before it reaches end users. Security monitoring should include detection of unusual memory access patterns and potential exploitation attempts, while user education programs should emphasize the importance of verifying document sources and avoiding suspicious PDF attachments. The vulnerability also highlights the need for regular security assessments of third-party software components and adherence to secure coding practices that prevent memory corruption issues. This particular case demonstrates how JavaScript engines embedded in document readers can become attack vectors when proper memory management protocols are not implemented, reinforcing the importance of following established security frameworks and standards such as those recommended by the Open Web Application Security Project and the Center for Internet Security.