CVE-2021-34832 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 the delay property. 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-13928.
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Analysis
by VulDB Data Team • 08/08/2021
CVE-2021-34832 represents a critical remote code execution vulnerability affecting Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic object validation flaw in software security architecture. This vulnerability resides within the PDF reader's handling of the delay property, where insufficient input validation permits attackers to manipulate object references without proper existence verification. The flaw directly maps to CWE-476 which describes NULL Pointer Dereference conditions, though in this case the vulnerability manifests through improper object validation rather than simple null pointer access. The attack requires user interaction through visiting malicious web pages or opening compromised PDF files, making it particularly dangerous in phishing scenarios where social engineering can be combined with technical exploitation. The vulnerability operates at the application level where the PDF reader processes delayed execution properties, and the lack of proper object validation creates a window for arbitrary code execution within the context of the running process. This presents a significant risk as the PDF reader typically runs with elevated privileges during document processing, potentially allowing attackers to escalate their privileges or execute malicious payloads with the same permissions as the legitimate application.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential system compromise and data exfiltration capabilities. Attackers leveraging this flaw can execute arbitrary commands on affected systems, potentially leading to full system compromise when combined with other exploitation techniques. The vulnerability's remote nature means that attackers can deploy malicious PDF files or web content without requiring physical access to target systems, making it particularly attractive for large-scale attacks. The exploitation process involves crafting malicious PDF content that triggers the delayed property handling mechanism, where the application attempts to perform operations on a non-existent object reference. This creates an exploitable condition that can be leveraged through various attack vectors including web-based delivery, email attachments, or malicious file sharing platforms. The vulnerability's classification aligns with ATT&CK technique T1203 which covers Exploitation for Client Execution, where adversaries gain access to execution capabilities on a victim's system through compromised applications or documents.
Mitigation strategies for CVE-2021-34832 must address both immediate remediation and long-term security hardening measures. Organizations should prioritize immediate patching of Foxit PDF Reader installations to version 11.0.1.49900 or later, as this represents the official vendor fix for the vulnerability. System administrators should implement network-based security controls including web proxies with content filtering and sandboxing solutions to prevent users from accessing potentially malicious PDF content. The vulnerability demonstrates the importance of input validation and object existence checking in security-critical applications, making defensive programming practices essential for preventing similar issues. Security teams should consider implementing application whitelisting policies to restrict PDF reader execution to trusted environments and monitor for unusual process behavior that might indicate exploitation attempts. Additionally, user education regarding the dangers of opening untrusted PDF files and visiting suspicious websites remains crucial in defending against social engineering components of this attack vector. Regular security assessments and vulnerability scanning should include checks for outdated PDF reader installations to prevent exploitation of this and similar vulnerabilities in the broader attack surface.