CVE-2021-34852 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-13929.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-34852 represents a critical remote code execution flaw in Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic improper input validation issue. This vulnerability falls under the CWE-476 category of NULL Pointer Dereference, where the software fails to validate that an object exists before attempting operations on it. The flaw specifically manifests within the Annotation object handling mechanism, which is a fundamental component of PDF documents used for adding comments, highlights, and other interactive elements to documents. The vulnerability's exploitation requires user interaction through visiting a malicious webpage or opening a malicious PDF file, making it particularly dangerous in phishing campaigns and targeted attacks where social engineering plays a crucial role in initial compromise.
The technical implementation of this vulnerability stems from inadequate object validation during PDF parsing operations. When Foxit PDF Reader processes Annotation objects within PDF files, the application does not properly verify whether referenced objects exist or are valid before attempting to access their properties or methods. This oversight creates a scenario where an attacker can craft a malicious PDF file containing specially constructed Annotation objects that reference non-existent or improperly initialized objects. When the vulnerable reader attempts to process these malformed objects, it triggers a NULL pointer dereference that can be exploited to execute arbitrary code with the privileges of the running process. The attack vector leverages the PDF rendering engine's failure to implement proper bounds checking and object validation mechanisms, which is a common pattern in memory corruption vulnerabilities.
From an operational impact perspective, this vulnerability presents a significant risk to organizations relying on Foxit PDF Reader for document processing and viewing. The remote code execution capability allows attackers to gain full control over affected systems without requiring any privileged access or additional exploitation steps beyond initial user interaction. The vulnerability affects the application's security model by enabling privilege escalation to the context of the current process, which typically runs with the same privileges as the user who opened the malicious document. This means that if an average user opens the malicious file, the attacker can execute code with the user's privileges, potentially leading to data theft, system compromise, or further network exploration. The vulnerability's classification as a remote attack vector significantly increases its threat potential as it does not require physical access or local network presence to exploit.
The exploitation of CVE-2021-34852 aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to initial access and execution phases. Attackers can leverage this vulnerability through techniques such as spearphishing with malicious PDF attachments or drive-by downloads from compromised websites. The vulnerability's characteristics make it particularly suitable for advanced persistent threat campaigns where attackers need to establish a foothold on target systems without detection. Security professionals should consider this vulnerability when implementing defensive measures, as it represents a common attack pattern that has been widely used in real-world exploitation scenarios. The vulnerability's impact extends beyond simple code execution to include potential data exfiltration, system reconnaissance, and lateral movement capabilities. Organizations should prioritize patching this vulnerability and implementing network monitoring to detect potential exploitation attempts, as the attack surface remains broad due to the widespread use of PDF readers across enterprise environments. The vulnerability also highlights the importance of input validation and proper error handling in software development processes, emphasizing that even seemingly benign features like annotation support can become attack vectors when proper validation mechanisms are absent.