CVE-2021-34844 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-14033.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-34844 represents a critical remote code execution flaw in Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic object validation error pattern. This weakness falls under the broader category of improper input validation and can be classified as CWE-476 which specifically addresses null pointer dereferences and similar validation failures. The vulnerability operates through the PDF reader's annotation handling mechanism where the application fails to properly validate whether objects exist before attempting to perform operations on them. This fundamental flaw in object lifecycle management creates an exploitable condition that allows attackers to manipulate the application's memory state through crafted PDF content. The security implications are particularly severe given that the vulnerability requires only user interaction through visiting a malicious webpage or opening a malicious file, making it highly vectorable in phishing campaigns and drive-by download scenarios.
The technical exploitation of this vulnerability leverages the absence of proper object existence checks within the annotation processing code path. When a PDF document contains specially crafted annotation objects, the Foxit reader attempts to process these elements without first verifying their structural integrity or existence. This validation gap creates a window where maliciously constructed data can cause the application to execute unintended code sequences within the context of the current process. The attack vector specifically targets the PDF parsing engine's handling of annotation objects, which are commonly used in PDF documents for adding notes, comments, and interactive elements. The flaw essentially allows an attacker to inject code that executes with the privileges and permissions of the currently running Foxit PDF Reader process, potentially leading to complete system compromise.
From an operational impact perspective, this vulnerability creates significant risk for organizations relying on Foxit PDF Reader for document handling and viewing. The requirement for user interaction makes it particularly dangerous in enterprise environments where users may inadvertently encounter malicious content through email attachments, web downloads, or shared network resources. The vulnerability's classification under ATT&CK technique T1203 (Exploitation for Client Execution) indicates its potential for lateral movement and privilege escalation within networked environments. Security teams must consider the widespread adoption of Foxit Reader across various industries, including finance, healthcare, and government sectors, where document security is paramount. The vulnerability's exploitation can result in unauthorized data access, system compromise, and potential data exfiltration, making it a high-priority target for threat actors seeking persistent access to organizational networks.
Organizations should implement immediate mitigations including updating to patched versions of Foxit PDF Reader where available, deploying network-based protections such as web application firewalls to filter malicious PDF content, and implementing user education programs to reduce successful exploitation attempts. The vulnerability underscores the importance of input validation and proper object handling in software development practices, particularly in security-sensitive applications like PDF readers that process untrusted content. Security professionals should also consider implementing sandboxing mechanisms for PDF processing and monitoring for unusual network activity that might indicate exploitation attempts. Additionally, regular vulnerability assessments and penetration testing should be conducted to identify similar validation gaps in other PDF processing components and third-party applications that handle untrusted document formats, as this type of vulnerability often indicates broader architectural weaknesses in input handling and validation routines.