CVE-2018-3946 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Software's 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-2018-3946 represents a critical use-after-free flaw within the JavaScript engine of Foxit PDF Reader version 9.1.0.5096, classified under CWE-416 which specifically addresses use of freed pointers in software systems. This vulnerability manifests when a maliciously crafted PDF document is processed by the vulnerable application, creating conditions where previously deallocated memory objects are accessed and reused, leading to potential arbitrary code execution. The flaw exists in the JavaScript engine's memory management mechanisms, where proper object lifecycle management fails to prevent access to memory that has already been freed, creating a dangerous scenario where attackers can manipulate program execution flow through controlled memory access patterns.
The operational impact of this vulnerability extends beyond simple user interaction requirements, as it operates through multiple attack vectors that align with techniques described in the MITRE ATT&CK framework under the T1203 category for exploitation of remote services. The vulnerability can be triggered through two primary methods: traditional file-based attacks where users must be tricked into opening a malicious PDF document, or more sophisticated web-based attacks when the browser plugin extension is enabled, allowing attackers to deliver malicious content through compromised websites. This dual attack surface significantly increases the exploitability of the vulnerability, as web-based delivery methods require less user interaction and can be automated at scale.
The technical exploitation of this use-after-free vulnerability involves careful crafting of PDF content that forces the JavaScript engine to execute specific memory management sequences, ultimately resulting in the reuse of freed memory objects. Attackers can leverage this flaw to overwrite critical memory locations with malicious code, potentially gaining full control over the victim's system. The vulnerability's presence in the JavaScript engine component of PDF processing software demonstrates the inherent risks associated with complex scripting environments that must handle untrusted input data. Memory corruption vulnerabilities of this nature often require sophisticated exploitation techniques that involve precise control over memory layout and object placement to achieve reliable code execution.
Mitigation strategies for CVE-2018-3946 should prioritize immediate software updates from Foxit to address the underlying memory management issues in their JavaScript engine implementation. Organizations should also implement defensive measures such as disabling the browser plugin extension when not required, implementing strict PDF file validation processes, and deploying application whitelisting controls to prevent execution of untrusted PDF content. Network-based protections should include web filtering solutions that can detect and block known malicious PDF patterns, while endpoint protection solutions should monitor for suspicious memory access patterns that may indicate exploitation attempts. The vulnerability underscores the importance of regular security updates and proper memory management practices in complex software systems, particularly those handling untrusted data inputs.