CVE-2021-34847 in Foxit
Summary
by MITRE • 08/04/2021
This vulnerability allows remote attackers to execute arbitrary code on affected installations of Foxit PDF Reader 11.0.0.49893. 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 Annotation 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-14270.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-34847 represents a critical remote code execution flaw in Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic null pointer dereference vulnerability pattern. This weakness specifically manifests within the PDF reader's annotation handling subsystem where the software fails to properly validate object existence before performing operations on annotation objects. The vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a well-documented software flaw that occurs when a program attempts to access a memory location through a pointer that has not been initialized to point to a valid object. The issue is particularly dangerous because it allows remote attackers to execute arbitrary code on vulnerable systems with minimal user interaction requirements.
The exploitation mechanism of this vulnerability relies on the attacker crafting a malicious PDF file containing specially constructed annotation objects that trigger the flawed validation logic. When the vulnerable Foxit PDF Reader processes such a file, it attempts to perform operations on annotation objects without first verifying their existence or proper initialization. This creates an execution path where a null pointer dereference occurs, leading to potential memory corruption and arbitrary code execution within the context of the current process. The attack vector requires user interaction through either visiting a malicious webpage that hosts the vulnerable PDF or opening a malicious file directly, making it particularly concerning for enterprise environments where users may encounter such content through phishing campaigns or compromised web resources.
From an operational impact perspective, this vulnerability presents a significant threat to organizations relying on Foxit PDF Reader for document processing and viewing. The remote code execution capability means that attackers can potentially gain full control of affected systems, escalate privileges, and establish persistent access points within network environments. The vulnerability affects the privilege context of the running application, which typically operates with the permissions of the user who launched the PDF reader, potentially leading to data exfiltration, system compromise, or lateral movement within corporate networks. The specific nature of the flaw within annotation object handling suggests that any PDF file containing crafted annotation data could serve as an attack vector, making it particularly challenging to defend against through simple network filtering or content inspection methods.
Security professionals should consider this vulnerability in the context of the MITRE ATT&CK framework, specifically under the T1059.007 technique for Command and Scripting Interpreter and potentially T1068 for Exploitation for Privilege Escalation. The vulnerability's impact aligns with the ATT&CK tactic of Execution and Persistence, as successful exploitation can lead to command execution and establishment of footholds within target environments. Organizations should implement immediate mitigations including prompt patching of Foxit PDF Reader to the latest version that addresses this vulnerability, network segmentation to limit exposure to potentially malicious PDF content, and user education to avoid opening suspicious PDF files or visiting untrusted websites. Additionally, security monitoring should be enhanced to detect unusual PDF processing activities that might indicate exploitation attempts, and endpoint protection solutions should be configured to scan PDF files for malicious annotation structures. The vulnerability also highlights the importance of proper input validation and object lifecycle management in software development practices, particularly for applications handling untrusted document formats.