CVE-2018-17626 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit Reader 9.2.0.9297. 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 Validate events of TextBox objects. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-6439.
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Analysis
by VulDB Data Team • 05/05/2020
This vulnerability in Foxit Reader version 9.2.0.9297 represents a critical remote code execution flaw that demonstrates poor input validation practices in document processing software. The vulnerability stems from insufficient object validation during the handling of Validate events for TextBox objects within the PDF rendering engine. This particular flaw falls under CWE-476 which specifically addresses NULL pointer dereferences and improper object validation in software applications. The vulnerability is particularly dangerous because it can be triggered through web-based attacks where users visit malicious websites containing specially crafted PDF content, or through direct file exploitation when users open compromised documents. The attack vector requires user interaction but does not demand sophisticated social engineering beyond normal browsing or document opening behavior.
The technical implementation of this vulnerability occurs when the Foxit Reader application processes PDF documents containing malicious TextBox objects with improperly validated Validate events. During normal PDF processing, the application attempts to perform operations on TextBox objects without first verifying whether these objects actually exist or have been properly initialized. This creates a classic null pointer dereference scenario where the application attempts to access memory locations that have not been allocated or properly validated. When the Validate event handler executes, it operates on what should be a valid object reference but instead encounters a null or invalid pointer, leading to unpredictable behavior that can be exploited by attackers to inject and execute arbitrary code within the application's memory space.
The operational impact of this vulnerability extends beyond simple code execution to potentially compromise entire user systems. Since the exploitation occurs within the context of the Foxit Reader process, attackers can leverage this to escalate privileges and gain access to sensitive user data, system resources, or even establish persistent backdoors. The vulnerability affects a widely deployed PDF reader application, making it particularly attractive to threat actors who can craft malicious websites or documents that automatically exploit this flaw. The fact that this vulnerability was tracked as ZDI-CAN-6439 indicates it was recognized by the Zero Day Initiative, highlighting its significance in the cybersecurity community and the potential for widespread exploitation across various organizations that rely on Foxit Reader for document processing.
Mitigation strategies for this vulnerability should focus on immediate patching of affected Foxit Reader installations, as the vendor would have released a security update addressing the Validate event handling logic. Network-based mitigations could include implementing web filtering solutions that block access to known malicious PDF content or using sandboxing technologies to isolate PDF processing activities. Organizations should also consider implementing user education programs to reduce the risk of visiting malicious websites or opening suspicious documents. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1203 which involves exploitation of web browsers and applications through malicious content, and T1059 which covers command and scripting interpreter usage for execution. System administrators should monitor for unusual process behavior or unexpected code execution patterns that might indicate exploitation attempts, while also implementing application whitelisting policies to prevent unauthorized code execution. The vulnerability underscores the importance of proper object validation and defensive programming practices in applications that process untrusted input data.