CVE-2018-3996 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Software's 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 • 07/31/2024
The vulnerability identified as CVE-2018-3996 represents a critical use-after-free condition within the JavaScript engine of Foxit PDF Reader version 9.2.0.9297, classified under CWE-416 as use of freed memory. This flaw occurs when the application processes specially crafted PDF documents that contain malicious JavaScript code designed to manipulate memory pointers and trigger the reuse of previously freed objects. The vulnerability stems from inadequate memory management practices within the JavaScript engine component that handles PDF document scripting, creating a scenario where memory addresses are not properly invalidated after object deallocation. The attack vector requires user interaction through opening a malicious PDF file, though the presence of browser plugin extensions expands the attack surface to include web-based delivery methods.
The technical exploitation of this vulnerability involves manipulating the JavaScript engine's memory allocation patterns to create a race condition where freed memory blocks are reallocated and accessed by subsequent operations. When a malicious PDF document is processed, the JavaScript engine executes code that causes specific objects to be freed from memory while maintaining references to them. Subsequent operations attempt to access these freed objects, leading to memory corruption that can be leveraged to execute arbitrary code with the privileges of the victim user. The vulnerability's exploitation requires precise control over memory layout and object lifecycle management within the PDF reader's JavaScript interpreter, making it particularly challenging to exploit but highly effective when successful. This type of vulnerability falls under the ATT&CK framework's technique T1059.007 for JavaScript and T1203 for Exploitation for Client Execution, demonstrating how malicious code can be executed through legitimate application interfaces.
The operational impact of CVE-2018-3996 extends beyond simple privilege escalation, as successful exploitation can result in complete system compromise and data exfiltration. Attackers can leverage this vulnerability to install backdoors, steal sensitive information, or establish persistent access to target systems through the PDF reader application. The vulnerability's prevalence in widely deployed PDF reader software makes it particularly attractive to threat actors, especially given the common use of PDF documents in corporate and government environments. Organizations using Foxit PDF Reader version 9.2.0.9297 face significant risk exposure, particularly in environments where users frequently open PDF attachments or visit untrusted websites with browser plugin extensions enabled. The vulnerability's trigger mechanism through user interaction makes social engineering attacks more effective, as users may unknowingly execute malicious code while performing routine document viewing tasks.
Mitigation strategies for CVE-2018-3996 should include immediate software updates to versions that address the memory management flaw, as well as implementing network-based security controls to filter malicious PDF content. Organizations should disable browser plugin extensions for PDF handling when possible, as these provide additional attack vectors beyond traditional file-based exploitation. System administrators should consider implementing application whitelisting policies to restrict PDF reader execution to trusted environments and establish user awareness training to reduce successful social engineering attempts. Network security measures such as web proxies and content filtering solutions should be configured to scan and block suspicious PDF documents before they reach end-user systems. The vulnerability highlights the importance of maintaining current security patches and implementing defense-in-depth strategies that reduce the attack surface for client-side exploits. Regular security assessments and penetration testing should include evaluation of JavaScript engine security to identify similar memory corruption vulnerabilities that may exist in other PDF processing applications.