CVE-2018-3994 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Software's Foxit PDF Reader version 9.2.0.9297. 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 to open 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 • 05/22/2023
The vulnerability identified as CVE-2018-3994 represents a critical use-after-free flaw within the JavaScript engine of Foxit PDF Reader version 9.2.0.9297, classified under CWE-416 as use of freed memory. This vulnerability stems from improper memory management practices where the JavaScript engine fails to properly track object references after memory deallocation, creating opportunities for malicious exploitation. The flaw specifically manifests when processing specially crafted PDF documents that contain malicious JavaScript code designed to trigger the use-after-free condition, making it particularly dangerous in the context of PDF reader software where users frequently encounter untrusted documents from various sources.
The technical exploitation of this vulnerability occurs through a carefully constructed PDF file that manipulates the JavaScript engine's memory management system. When the vulnerable PDF reader processes such a document, the JavaScript engine executes code that causes a specific object to be freed from memory while maintaining references to it. Subsequently, when the application attempts to access this previously freed memory location, it can be reused for malicious purposes, allowing attackers to execute arbitrary code with the privileges of the victim user. The vulnerability is particularly insidious because it can be triggered through multiple vectors including direct file opening or through browser plugin extensions when visiting malicious websites, expanding the attack surface significantly.
The operational impact of CVE-2018-3994 extends beyond simple code execution, as it can lead to complete system compromise when attackers leverage this vulnerability. The use-after-free condition allows for memory corruption that can be exploited to overwrite critical memory locations, potentially leading to privilege escalation or the installation of persistent backdoors. This vulnerability particularly affects enterprise environments where PDF documents are commonly shared and opened by multiple users, making it a prime target for advanced persistent threats. The fact that browser plugin extensions can trigger the vulnerability means that users may be compromised simply by visiting malicious websites, without needing to download or open any files directly.
Organizations should implement multiple layers of defense to mitigate this vulnerability, including immediate patching of Foxit PDF Reader to versions that address the memory management flaw. The ATT&CK framework categorizes this type of vulnerability under T1059.007 for JavaScript and T1203 for exploitation of remote services, emphasizing the need for both endpoint protection and network monitoring. Security measures should include disabling JavaScript execution in PDF readers when not required, implementing strict file validation policies, and conducting regular security assessments of PDF handling systems. Network segmentation and web filtering solutions can help prevent access to malicious sites that may host exploit code, while regular security awareness training can help users recognize potentially malicious PDF documents. The vulnerability highlights the importance of maintaining up-to-date software and the risks associated with browser plugin extensions that extend the attack surface of applications.