CVE-2018-16293 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Reader before 9.3 and PhantomPDF before 9.3, a different vulnerability than CVE-2018-16291, CVE-2018-16292, CVE-2018-16294, CVE-2018-16295, CVE-2018-16296, and CVE-2018-16297. 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 • 07/31/2024
The vulnerability described in CVE-2018-16293 represents a critical use-after-free flaw within the JavaScript engine of Foxit Reader and PhantomPDF applications. This issue affects versions prior to 9.3 and operates through a sophisticated memory management exploit that leverages the improper handling of object references in the PDF rendering engine. The vulnerability specifically targets the JavaScript interpreter component that processes PDF documents, creating conditions where previously deallocated memory objects can be accessed and manipulated by malicious code. The flaw demonstrates a fundamental weakness in the application's memory management protocols, where the system fails to properly invalidate object references after memory deallocation, leading to potential code execution opportunities. This type of vulnerability falls under the CWE-416 category, which specifically addresses use-after-free conditions, making it a well-documented and dangerous class of memory safety issues that have been extensively studied in cybersecurity research.
The technical exploitation of this vulnerability occurs when a malicious PDF document is crafted to trigger a specific sequence of operations within the JavaScript engine. The attacker creates a PDF that, when processed by the vulnerable software, causes the engine to free a memory object while maintaining references to it. Subsequently, the application attempts to reuse this freed memory location, which may have been overwritten with attacker-controlled data. This memory reuse allows for arbitrary code execution because the application treats the overwritten memory as valid object data rather than as corrupted memory. The exploit requires user interaction through opening the malicious file, but when combined with browser plugin extensions, it can be triggered through web navigation, expanding the attack surface significantly. The JavaScript engine's handling of complex object lifecycles and reference counting mechanisms becomes the primary attack vector, as the system fails to properly track when objects are no longer valid for use.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise when successfully exploited. An attacker who successfully triggers this vulnerability can gain full control over the victim's system, potentially leading to data theft, persistent backdoor installation, or further network infiltration. The vulnerability's exploitation is particularly concerning because it can be delivered through standard PDF documents, which are commonly encountered in business environments, making it an attractive target for social engineering campaigns. The attack vector through browser plugins increases the risk profile significantly, as web-based attacks can be more easily automated and distributed. Organizations using these vulnerable applications face potential exposure to advanced persistent threats that could leverage this vulnerability to establish long-term presence within their networks. The impact is amplified by the fact that PDF documents are frequently shared through legitimate business channels, making user awareness and training critical components of defense strategies.
Mitigation strategies for CVE-2018-16293 primarily focus on immediate software updates and security configuration adjustments. The most effective immediate solution involves upgrading Foxit Reader and PhantomPDF to version 9.3 or later, where the memory management issues have been addressed through improved object reference tracking and memory deallocation procedures. Organizations should implement strict document validation policies that scan PDF files for potentially malicious content before processing, particularly when dealing with external or untrusted sources. Network-based security controls such as web application firewalls and content filtering systems can help prevent access to known malicious websites that might host exploit code. Additionally, disabling browser plugin extensions that interface with PDF rendering capabilities can significantly reduce the attack surface, as this eliminates one of the primary exploitation vectors. Security teams should also consider implementing sandboxing mechanisms that isolate PDF processing operations from the main system, limiting the potential damage from successful exploitation attempts. The vulnerability's classification under ATT&CK technique T1203 - Exploitation for Client Execution demonstrates its alignment with established threat modeling frameworks, reinforcing the need for comprehensive defensive measures that address both endpoint and network-level protections.