CVE-2021-34837 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-14018.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-34837 represents a critical remote code execution flaw in Foxit PDF Reader version 11.0.0.49893, demonstrating a classic object validation weakness that has significant implications for document security. This vulnerability falls under the CWE-476 category of NULL Pointer Dereference, where the software fails to properly validate object existence before attempting operations on them. The flaw specifically manifests within the annotation handling subsystem, which is a fundamental component of PDF document processing that allows for interactive elements, comments, and markup features. The attack vector requires user interaction, making it particularly dangerous as it can be delivered through malicious websites or compromised PDF files that users might legitimately open, creating a social engineering component that amplifies the threat landscape.
The technical exploitation of this vulnerability occurs when the PDF reader processes annotation objects that have not been properly validated for existence or integrity. When the application attempts to perform operations on these uninitialized or corrupted annotation objects, it creates a condition where memory corruption can occur, potentially allowing an attacker to inject and execute arbitrary code within the context of the current process. This type of vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute code on target systems. The lack of proper input validation and object existence checking creates a pathway for attackers to manipulate the application's memory structure, potentially leading to privilege escalation or complete system compromise depending on the execution context and user privileges.
The operational impact of CVE-2021-34837 extends beyond simple code execution, as it represents a fundamental flaw in how Foxit PDF Reader handles potentially malicious input data. This vulnerability affects organizations that rely heavily on PDF document processing, particularly those in sectors where document security is paramount such as legal, financial, and government institutions. The requirement for user interaction means that traditional network-based defenses may not prevent exploitation, making user education and awareness critical components of defense. Organizations running vulnerable versions of Foxit PDF Reader face potential data breaches, system compromise, and unauthorized access to sensitive information, with the attack surface expanding to include web-based delivery mechanisms and email attachments. The vulnerability's classification as a remote code execution flaw means that attackers can potentially establish persistent access to compromised systems, making this a high-priority remediation item for enterprise security teams.
Mitigation strategies for CVE-2021-34837 should focus on immediate patch management, as the vulnerability has been addressed through official updates from Foxit Corporation. Organizations should implement network segmentation and web filtering to prevent access to known malicious domains and files, while also deploying endpoint protection solutions that can detect anomalous behavior patterns associated with exploitation attempts. The implementation of principle of least privilege should be enforced, ensuring that PDF reader applications run with minimal required permissions to reduce potential impact from successful exploitation. Security monitoring should include detection of unusual PDF processing activities and memory access patterns that might indicate exploitation attempts. Additionally, organizations should conduct regular vulnerability assessments and penetration testing to identify similar validation flaws in other document processing applications, as this vulnerability type represents a common class of issues that can affect various PDF readers and document processing frameworks. The vulnerability also highlights the importance of input validation and object lifecycle management in software development practices, emphasizing the need for comprehensive security testing and code review processes that address these fundamental validation requirements.