CVE-2019-6734 in PhantomPDF
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on vulnerable installations of Foxit PhantomPDF. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the handling of the setInterval method. By performing actions in JavaScript, an attacker can cause a pointer to be reused after it has been freed. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the current process. Was ZDI-CAN-7452.
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Analysis
by VulDB Data Team • 08/04/2023
The CVE-2019-6734 vulnerability represents a critical memory corruption issue affecting Foxit PhantomPDF installations, specifically targeting the JavaScript engine's handling of the setInterval method. This vulnerability falls under the category of use-after-free conditions as classified by CWE-416, where a pointer is accessed after the memory it references has been deallocated. The flaw manifests when the PDF reader processes JavaScript code containing setInterval calls, creating a scenario where memory management becomes compromised. The vulnerability requires user interaction to be exploited, meaning an attacker must convince a victim to visit a malicious webpage or open a specially crafted PDF file containing the malicious JavaScript payload. This social engineering component aligns with common attack patterns documented in the MITRE ATT&CK framework under the initial access phase, specifically leveraging phishing techniques to deliver malicious content.
The technical exploitation of this vulnerability occurs through JavaScript manipulation that forces the reuse of a freed memory pointer, creating a condition where the application attempts to access memory that has already been released back to the system. When the setInterval method is invoked with specific parameters, it triggers a memory management error that allows for pointer reuse, potentially enabling attackers to control the execution flow of the application. The memory corruption aspect of this vulnerability is particularly dangerous because it can be leveraged as a stepping stone for more severe exploits, including arbitrary code execution within the context of the current process. This type of vulnerability represents a classic heap-based memory corruption issue that has been frequently documented in security research and is commonly exploited in advanced persistent threat campaigns.
The operational impact of CVE-2019-6734 extends beyond simple information disclosure, as it provides a potential pathway for full system compromise when combined with other vulnerabilities present in the target environment. Attackers can exploit this flaw to execute malicious code with the privileges of the PhantomPDF process, which typically runs with elevated permissions when interacting with PDF documents. The vulnerability's reliance on JavaScript-based exploitation makes it particularly insidious as it can be delivered through web-based attacks, email attachments, or file-sharing platforms where users might encounter malicious PDF documents. Organizations using Foxit PhantomPDF are at risk of targeted attacks where adversaries leverage this vulnerability as part of a multi-stage attack vector, potentially leading to data breaches, privilege escalation, or complete system compromise. The vulnerability's classification as a remote code execution risk places it in the high-severity category according to industry security standards and requires immediate attention from security teams responsible for protecting enterprise environments.
Mitigation strategies for CVE-2019-6734 should focus on both immediate patching and operational security measures to reduce the attack surface. Organizations must prioritize applying the vendor-provided security patches as soon as they become available, as this vulnerability has been widely documented and actively exploited in the wild. Network-based protections such as web application firewalls and content filtering solutions can help detect and block malicious JavaScript payloads before they reach users, though these measures are not foolproof given the sophisticated nature of modern attacks. User education remains critical in defending against this vulnerability, as training personnel to recognize suspicious email attachments and web links can significantly reduce successful exploitation attempts. Additionally, implementing application whitelisting policies that restrict the execution of unauthorized PDF readers or JavaScript-based applications can provide an additional layer of defense. Security monitoring should include detection of unusual JavaScript behavior patterns and memory access violations that might indicate exploitation attempts, while endpoint protection solutions should be configured to alert on suspicious file execution patterns related to PDF processing. The vulnerability's nature as a memory corruption issue also suggests that implementing modern exploit mitigation techniques such as address space layout randomization and data execution prevention can help reduce the effectiveness of exploitation attempts even if patches are not immediately available.