CVE-2018-3967 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Software's Foxit PDF Reader version 9.1.0.5096. 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 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-2018-3967 represents a critical use-after-free flaw within the JavaScript engine of Foxit PDF Reader version 9.1.0.5096, classified under CWE-416 as Use After Free. This vulnerability arises from improper memory management practices where the JavaScript engine fails to properly track object lifecycles, allowing previously freed memory locations to be accessed and reused. The flaw specifically manifests during PDF document processing when the engine encounters malformed JavaScript code that triggers the reuse of freed memory objects, creating a potential exploitation vector for remote code execution.
The technical exploitation of this vulnerability requires an attacker to craft a malicious PDF document that specifically targets the JavaScript engine's memory management routines. When the vulnerable application processes such a document, the JavaScript engine executes code that causes a memory object to be freed from the heap, but subsequent code execution attempts to access this freed memory location. This memory corruption scenario enables attackers to manipulate the program's execution flow and potentially execute arbitrary code with the privileges of the user running the PDF reader. The vulnerability is particularly dangerous because it can be triggered through multiple attack vectors including direct file opening and web browser plugin execution, expanding the potential attack surface significantly.
The operational impact of CVE-2018-3967 extends beyond simple remote code execution to encompass full system compromise capabilities. The vulnerability's exploitation can lead to complete system takeover, data exfiltration, and persistence mechanisms within the victim's environment. Attackers can leverage this flaw to install malware, establish backdoors, or conduct further reconnaissance activities. The fact that browser plugin extensions can trigger this vulnerability means that users are at risk even when browsing legitimate websites, as malicious actors can host exploit code on compromised sites or use drive-by download techniques to deliver the malicious PDF documents. This makes the vulnerability particularly concerning for enterprise environments where users frequently access untrusted web content.
Mitigation strategies for CVE-2018-3967 primarily focus on immediate patching and application hardening measures. Organizations should prioritize updating Foxit PDF Reader to versions that contain memory management fixes and proper object lifecycle handling. System administrators should disable JavaScript execution in PDF readers when possible, as this significantly reduces the attack surface for this specific vulnerability. Network-based protections such as web application firewalls and content filtering systems can help detect and block malicious PDF content before it reaches end users. Additionally, user education regarding the risks of opening unknown PDF files and visiting untrusted websites remains crucial. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for JavaScript-based execution and T1068 for privilege escalation, with potential lateral movement capabilities once initial compromise is achieved. Security monitoring should focus on detecting unusual memory access patterns and process behavior anomalies that may indicate exploitation attempts.