CVE-2021-34849 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-14531.
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Analysis
by VulDB Data Team • 08/08/2021
CVE-2021-34849 represents a critical remote code execution vulnerability affecting Foxit PDF Reader version 11.0.0.49893, classified under CWE-476 as a null pointer dereference vulnerability. This weakness occurs within the PDF reader's annotation object handling mechanism where the software fails to validate whether an object exists before attempting operations on it. The vulnerability stems from inadequate input validation and object lifecycle management, creating a condition where maliciously crafted PDF files can trigger unauthorized code execution. Attackers exploit this by crafting specially designed annotation objects that, when processed by the vulnerable software, cause the application to attempt operations on non-existent objects, leading to memory corruption and potential code execution.
The operational impact of this vulnerability extends beyond simple remote code execution, as it allows attackers to operate within the security context of the currently running process, potentially escalating privileges or accessing sensitive system resources. The requirement for user interaction through visiting malicious web pages or opening malicious files aligns with ATT&CK technique T1203, which involves user interaction as a prerequisite for exploitation. This makes the vulnerability particularly dangerous in targeted attack scenarios where social engineering can be employed to deliver malicious PDF content. The vulnerability's presence in the annotation handling code path indicates a broader class of issues related to improper object validation and memory management within PDF processing libraries.
Security professionals must understand that this vulnerability represents a fundamental flaw in the application's defensive programming practices, specifically in object validation and error handling mechanisms. The lack of proper null checks before object operations creates a predictable exploitation pattern that can be automated by threat actors. Organizations should implement immediate mitigations including disabling PDF preview features in web browsers, implementing strict file type filtering, and deploying network-based intrusion detection systems to monitor for suspicious PDF content. The vulnerability also highlights the importance of regular security updates and patch management, as this issue was addressed through subsequent software releases that properly validate object existence before processing operations. Additionally, security awareness training should emphasize the dangers of opening untrusted PDF files and visiting suspicious websites, since the exploitation requires user interaction to be successful.