CVE-2021-34845 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-14034.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-34845 represents a critical remote code execution flaw in Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic object validation error pattern commonly found in software applications handling complex file formats. This vulnerability operates under the CWE-476 principle of null pointer dereference, where the application fails to properly validate the existence of Annotation objects before attempting to process them. The flaw specifically manifests within the PDF parsing engine's annotation handling subsystem, where the software does not adequately verify whether referenced objects exist in memory before executing operations against them.
The exploitation mechanism requires user interaction through either visiting a malicious webpage or opening a crafted PDF file containing specially constructed Annotation objects. This user interaction requirement places the vulnerability in the ATT&CK matrix under technique T1203 - Exploitation for Client Execution, which emphasizes the need for social engineering or phishing campaigns to deliver the malicious payload. The attack vector leverages the PDF reader's legitimate functionality to process annotations, which are commonly used in collaborative documents and forms, making the attack surface more accessible to potential victims.
When an attacker crafts a malicious PDF file with improperly validated Annotation objects, the Foxit PDF Reader application attempts to process these objects without proper validation checks, leading to a situation where the application may attempt to execute code on the victim's system with the privileges of the current user process. This represents a significant escalation from a simple parsing error to a full remote code execution capability, as the application's memory management system becomes compromised during the annotation processing phase. The vulnerability affects the application's security model by allowing arbitrary code execution in the context of the running process, which could potentially lead to system compromise if the application runs with elevated privileges.
The operational impact of this vulnerability extends beyond simple code execution, as it can be leveraged to establish persistent access, escalate privileges, or serve as a foothold for further attacks within a network environment. Attackers can utilize this vulnerability to deploy malware, establish backdoors, or perform data exfiltration without requiring direct system access. The vulnerability's classification under ZDI-CAN-14034 indicates it was recognized by the Zero Day Initiative and prioritized as a critical threat, highlighting its potential for widespread exploitation across organizations relying on Foxit PDF Reader for document processing. Organizations should immediately implement mitigations including disabling PDF plugin execution, updating to patched versions, and deploying network-based intrusion detection systems to monitor for exploitation attempts.
This vulnerability demonstrates the critical importance of input validation and object lifecycle management in document processing applications, particularly those handling complex binary formats like PDFs. The flaw serves as a reminder of the inherent security risks present in applications that must parse and render complex file formats, where improper validation of object references can lead to complete system compromise. Security teams should conduct comprehensive vulnerability assessments of all PDF processing applications within their environments, as similar patterns may exist in other software that handles complex document formats or rich media content. The vulnerability's characteristics align with common attack patterns described in the OWASP Top Ten and NIST cybersecurity frameworks, emphasizing the need for robust application security practices and regular security assessments to prevent similar issues from arising in other software components.