CVE-2018-3995 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 • 05/22/2023
The vulnerability CVE-2018-3995 represents a critical use-after-free flaw within Foxit PDF Reader's JavaScript engine, specifically affecting version 9.2.0.9297. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating a scenario where subsequent operations on that memory location can lead to unpredictable behavior including code execution. The flaw manifests in the JavaScript engine's handling of memory management during PDF document processing, where improper object lifecycle management allows attackers to manipulate freed memory structures. The vulnerability is particularly concerning because it operates at the core of PDF reader functionality, where JavaScript execution is commonly enabled for interactive documents and form processing. 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 exploitation when users visit compromised websites.
The technical implementation of this vulnerability stems from improper memory management within the JavaScript engine's object reference counting or garbage collection mechanisms. When processing certain PDF documents, the engine allocates memory for JavaScript objects and subsequently frees them when they are no longer referenced. However, a flaw exists in the reference tracking system that allows these freed objects to remain accessible through indirect references or delayed cleanup operations. Attackers can craft malicious PDF documents that manipulate the JavaScript engine's memory state by creating specific object relationships and triggering conditions that cause the freed memory to be reallocated and reused. This process typically involves creating a scenario where the JavaScript engine's garbage collector or memory management subsystem fails to properly track object lifecycles, leading to a situation where freed memory chunks are repurposed for new objects while still containing references to the original object's structure. The vulnerability is categorized under CWE-416 as use-after-free, which is a well-known class of memory safety issues that frequently leads to remote code execution in browser and document processing applications.
The operational impact of CVE-2018-3995 extends beyond simple privilege escalation to encompass full system compromise when exploited successfully. An attacker who successfully triggers this vulnerability can execute arbitrary code with the privileges of the PDF reader application, typically running with user-level permissions but potentially elevated through privilege escalation techniques. The vulnerability's exploitation capability aligns with ATT&CK technique T1059.007 for JavaScript execution, demonstrating how PDF-based attack vectors can leverage scripting capabilities to achieve malicious objectives. The attack requires social engineering to convince victims to open malicious documents, but the browser plugin extension component makes it possible to exploit through web-based attacks, expanding the threat surface significantly. Organizations that rely heavily on PDF document processing, particularly those with enabled browser plugins, face elevated risk exposure as this vulnerability can be triggered through web browsing activities without requiring direct file interaction. The vulnerability's presence in a widely used PDF reader application means that successful exploitation can lead to data exfiltration, system compromise, or deployment of additional malware payloads.
Mitigation strategies for CVE-2018-3995 must address both immediate defensive measures and long-term architectural improvements to prevent similar vulnerabilities. The most effective immediate solution involves updating to Foxit PDF Reader version 9.2.1 or later, where the memory management flaws have been corrected through proper object lifecycle handling and reference tracking improvements. Organizations should also implement strict PDF document handling policies that limit JavaScript execution in untrusted documents and consider deploying PDF sandboxing solutions to contain potential exploitation attempts. Network-level defenses can include PDF content filtering and web proxy configurations that block suspicious PDF content or restrict access to known malicious domains. Security teams should monitor for exploitation attempts through endpoint detection and response systems, particularly looking for unusual JavaScript engine behavior or memory allocation patterns. The vulnerability highlights the importance of secure coding practices in memory management, specifically the need for proper object reference counting and the implementation of memory safety techniques such as those recommended in the CERT Secure Coding Standards for C and C++. Additionally, organizations should consider implementing application whitelisting to restrict execution of unauthorized PDF reader versions and establish regular patch management processes to ensure timely deployment of security updates. The ATT&CK framework suggests that defensive measures should include process monitoring and anomaly detection to identify potential exploitation attempts through JavaScript engine manipulation.