CVE-2018-3966 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-2018-3966 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 improper cleanup of memory resources. This vulnerability stems from inadequate memory management practices where the JavaScript engine fails to properly track object references after memory deallocation, creating opportunities for malicious code execution through memory corruption attacks. The flaw specifically manifests when processing specially crafted PDF documents that contain malicious JavaScript code designed to exploit the memory management inconsistency. The vulnerability operates at the intersection of software security and browser-based attack vectors, making it particularly dangerous in environments where PDF documents are frequently opened or viewed through web browsers with Foxit plugin extensions enabled.
The technical implementation of this vulnerability involves a complex interplay between memory management and JavaScript execution contexts within the Foxit PDF Reader application. When a malicious PDF document is processed, the JavaScript engine executes code that triggers the freeing of specific memory objects while maintaining references to them. Subsequently, when the same memory locations are reallocated and accessed, the attacker-controlled code can manipulate the freed object's contents to redirect execution flow. This exploitation technique aligns with common memory corruption attack patterns documented in the ATT&CK framework under T1059.007 for JavaScript and T1203 for exploitation of memory corruption vulnerabilities. The flaw demonstrates how improper memory management in complex software applications can create persistent attack surfaces that remain exploitable across multiple execution contexts.
The operational impact of CVE-2018-3966 extends beyond simple privilege escalation to encompass full system compromise capabilities when successfully exploited. An attacker can leverage this vulnerability to execute arbitrary code with the privileges of the affected user, potentially leading to complete system takeover through privilege escalation techniques. The attack vector requires user interaction through opening malicious PDF files, making it particularly effective in phishing campaigns where social engineering plays a crucial role. Additionally, when the browser plugin extension is enabled, the vulnerability becomes exploitable through web-based attacks, expanding the attack surface to include web browsers and online content delivery. The vulnerability's persistence across different execution contexts makes it particularly challenging to defend against, as it can be triggered both through local file execution and remote web-based attacks.
Mitigation strategies for CVE-2018-3966 should encompass both immediate patching procedures and defensive operational measures. The primary recommendation involves applying the official security patches released by Foxit Software to address the memory management flaws within the JavaScript engine. Organizations should also implement strict document filtering policies that prevent the opening of untrusted PDF files, particularly those received through email or downloaded from unverified sources. Network-level defenses including web proxies and content filtering systems should be configured to block potentially malicious PDF content and JavaScript execution within PDF documents. Security monitoring should include detection of unusual JavaScript behavior and memory access patterns that may indicate exploitation attempts. The vulnerability's characteristics also suggest implementing application whitelisting measures and restricting PDF reader functionality in web browsers to minimize the attack surface. Regular security assessments and penetration testing should be conducted to identify similar memory management flaws in other software applications, as this vulnerability type remains prevalent in complex software systems.