CVE-2021-34853 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-14013.
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Analysis
by VulDB Data Team • 08/08/2021
CVE-2021-34853 represents a critical remote code execution vulnerability in Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic improper input validation flaw categorized under CWE-476. This vulnerability resides within the annotation object handling mechanism of the PDF reader, where the software fails to validate whether an object exists before performing operations on it. The flaw constitutes a NULL pointer dereference vulnerability that can be exploited by attackers who craft malicious PDF files containing specially constructed annotation objects. The vulnerability requires user interaction to be successful, meaning that victims must either visit a malicious webpage hosting the exploit or open a crafted malicious PDF file to trigger the vulnerability.
The technical exploitation of this vulnerability occurs when the PDF reader processes annotation objects without proper validation checks, allowing an attacker to manipulate the object reference chain and subsequently execute arbitrary code within the context of the current process. This type of vulnerability falls under the ATT&CK framework category of T1059 Command and Scripting Interpreter, where attackers leverage legitimate system processes to execute malicious code. The lack of proper object existence validation creates a path for attackers to manipulate memory structures and potentially escalate privileges or execute malicious payloads with the same privileges as the PDF reader application.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with a persistent foothold within targeted environments where Foxit PDF Reader is installed. The vulnerability affects organizations that rely on PDF document processing, particularly those that do not maintain strict controls over PDF file downloads or web browsing activities. Attackers can leverage this vulnerability to deploy malware, establish backdoors, or conduct further reconnaissance within the compromised network. The vulnerability's classification as a remote code execution flaw means that attackers can exploit it without requiring physical access to the target system, making it particularly dangerous in enterprise environments where PDF documents are frequently shared and opened.
Organizations should immediately implement mitigations including updating to the latest version of Foxit PDF Reader where the vulnerability has been patched, implementing strict PDF file validation policies, and deploying network-based intrusion detection systems to monitor for suspicious PDF file transfers. Security teams should also consider implementing application whitelisting controls to restrict execution of untrusted PDF files and establishing user education programs to raise awareness about the risks of opening suspicious PDF documents. The vulnerability serves as a reminder of the importance of proper input validation and object-oriented programming practices in security-critical applications, particularly those handling untrusted data such as PDF documents.