CVE-2018-3993 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Software's Foxit PDF Reader version 9.2.0.9297. 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 identified as CVE-2018-3993 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 arises from improper memory management where the JavaScript engine fails to properly track object references after memory deallocation, creating opportunities for attackers to manipulate freed memory locations. The vulnerability exists specifically within the PDF rendering engine's JavaScript interpretation capabilities, making it particularly dangerous in environments where PDF documents are frequently opened or viewed through web browsers with embedded PDF plugins.
The technical exploitation of this vulnerability occurs when a malicious PDF document contains specially crafted JavaScript code that triggers a sequence leading to memory corruption. During normal PDF processing, certain JavaScript objects are allocated and subsequently freed from memory, but the engine does not adequately invalidate references to these objects. When the malicious code executes, it can cause the freed memory to be reallocated and then accessed again, leading to a use-after-free condition that can be leveraged for arbitrary code execution. This type of vulnerability is particularly insidious because it can be triggered through multiple vectors including direct file opening or through web browser plugin execution, expanding the attack surface significantly.
The operational impact of CVE-2018-3993 extends beyond simple privilege escalation or denial of service scenarios, as it provides full arbitrary code execution capabilities to remote attackers. This vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where attackers can leverage browser-based attacks to execute malicious code on target systems. The attack requires minimal user interaction beyond opening the malicious PDF file or visiting a compromised website, making it particularly effective in phishing campaigns or drive-by download scenarios. Organizations running Foxit PDF Reader 9.2.0.9297 are at significant risk as this vulnerability can be exploited without requiring elevated privileges, potentially allowing attackers to install malware, steal sensitive data, or establish persistent access to compromised systems.
Mitigation strategies for this vulnerability should focus on immediate software updates and user education. The primary recommendation is to upgrade to Foxit PDF Reader version 9.3.0.9300 or later, which contains the necessary memory management fixes to prevent the use-after-free condition. Additionally, implementing browser security policies that disable JavaScript execution in PDF plugins, employing sandboxing techniques, and maintaining strict email filtering controls can significantly reduce the risk of exploitation. Network-based protections such as web application firewalls and intrusion prevention systems should be configured to detect and block malicious PDF content. Organizations should also conduct regular security awareness training to educate users about the dangers of opening suspicious PDF files and visiting untrusted websites, as social engineering remains a critical component of successful exploitation attempts for this type of vulnerability.