CVE-2018-3850 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine Foxit Software Foxit PDF Reader version 9.0.1.1049. 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 a browser plugin extension is enabled, visiting a malicious site can also trigger the vulnerability.
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Analysis
by VulDB Data Team • 03/03/2023
The vulnerability identified as CVE-2018-3850 represents a critical use-after-free flaw within the JavaScript engine of Foxit PDF Reader version 9.0.1.1049. This type of vulnerability occurs when a program continues to reference memory locations that have already been freed, creating opportunities for attackers to manipulate program execution flow. The flaw specifically affects the handling of JavaScript objects within PDF documents, making it particularly dangerous in the context of PDF readers that execute JavaScript code. The vulnerability is classified under CWE-416 as a use-after-free condition, which is a well-known class of memory safety issues that have historically led to numerous exploitation techniques including arbitrary code execution.
The technical implementation of this vulnerability involves the JavaScript engine's improper memory management during object lifecycle handling. When processing specially crafted PDF documents containing malicious JavaScript code, the engine fails to properly track object references, allowing previously deallocated memory to be accessed and modified. This memory corruption occurs during the normal execution flow of JavaScript within the PDF context, where the engine's garbage collection mechanism or reference counting system becomes inconsistent. The flaw enables attackers to place controlled data at the memory location of the freed object, which then gets dereferenced during subsequent operations, providing a path for code execution.
The operational impact of CVE-2018-3850 extends beyond simple privilege escalation to full system compromise, as the vulnerability allows for arbitrary code execution with the privileges of the user running the PDF reader. This makes it particularly attractive to threat actors seeking to establish persistent access or deploy malware payloads. The attack vector requires user interaction through opening malicious PDF files, which can be delivered via email attachments, malicious websites, or compromised documents. When browser plugin extensions are enabled, the vulnerability can be triggered simply by visiting a malicious website, expanding the attack surface significantly. The exploitation process typically involves crafting a PDF document with JavaScript that creates the conditions for memory corruption, followed by the execution of malicious code that takes advantage of the freed object's memory location.
Mitigation strategies for CVE-2018-3850 should prioritize immediate patching of affected Foxit PDF Reader versions, as the vendor has released updates addressing this specific vulnerability. Organizations should implement strict document handling policies, including sandboxing PDF reading operations and restricting JavaScript execution within PDF documents. Network-level protections such as web application firewalls and content filtering systems can help prevent access to known malicious PDF content. Security monitoring should focus on detecting unusual PDF processing activities and potential exploitation attempts. The vulnerability demonstrates the importance of proper memory management in software applications and aligns with ATT&CK technique T1203 for legitimate program execution and T1059 for command and scripting interpreter, highlighting how such flaws can be leveraged for broader attack chains. Additionally, the vulnerability reinforces the necessity of regular security assessments and vulnerability management programs to identify and remediate similar memory safety issues in software applications.