CVE-2021-34846 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-14120.
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Analysis
by VulDB Data Team • 08/08/2021
This vulnerability in Foxit PDF Reader 11.0.0.49893 represents a critical remote code execution flaw that demonstrates poor input validation practices in PDF annotation processing. The vulnerability stems from insufficient object validation within the annotation handling mechanism, creating a dangerous condition where the software attempts to operate on objects that may not exist or have been improperly initialized. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereferences and improper object validation. The flaw exists in the PDF parsing engine's annotation subsystem where the application fails to verify that annotation objects are properly instantiated before executing operations on them, creating a path for malicious code injection through crafted PDF documents.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise when exploited successfully. Attackers can craft malicious PDF files containing specially constructed annotation objects that trigger the validation gap during document rendering, allowing arbitrary code execution with the privileges of the running Foxit process. This represents a significant risk to enterprise environments where PDF readers are frequently used for document sharing and collaboration. The requirement for user interaction through visiting malicious web pages or opening malicious files aligns with ATT&CK technique T1203 which describes exploitation of web browsers and PDF readers through social engineering. The vulnerability essentially transforms the PDF reader into an attack vector that can be leveraged for privilege escalation, data exfiltration, or further network infiltration.
Organizations must implement immediate mitigations to protect against exploitation of this vulnerability, including prompt patching of Foxit PDF Reader to version 11.0.1.49905 or later which addresses the object validation issue. Network segmentation and web filtering solutions should be enhanced to block access to suspicious PDF content, while user education programs should emphasize the dangers of opening untrusted PDF files from unknown sources. The vulnerability demonstrates the critical importance of input validation and defensive programming practices, particularly in software handling untrusted data such as PDF documents. Security teams should monitor for indicators of compromise including unusual network connections or process execution patterns that may suggest exploitation attempts, while also implementing application whitelisting policies to restrict PDF reader execution to trusted environments. This vulnerability serves as a reminder of how seemingly minor validation gaps can create significant security risks in widely deployed software applications.