CVE-2019-6773 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on vulnerable installations of Foxit Reader 9.4.1.16828. 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 the richValue property of a Field object within AcroForms. 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 in conjunction with other vulnerabilities to execute code in the context of the current process. Was ZDI-CAN-8272.
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Analysis
by VulDB Data Team • 09/26/2023
The vulnerability identified as CVE-2019-6773 represents a critical information disclosure flaw within Foxit Reader version 9.4.1.16828 that exposes systems to remote exploitation. This vulnerability operates through the manipulation of AcroForm field objects, specifically targeting the richValue property of Field objects during PDF document processing. The flaw stems from insufficient input validation mechanisms that fail to verify object existence before executing operations on them, creating a dangerous condition where attackers can exploit uninitialized or improperly validated objects. This type of vulnerability falls under CWE-476 which specifically addresses NULL Pointer Dereferences, where the absence of proper null checks leads to system instability and potential information leakage. The attack vector requires user interaction through either visiting a malicious webpage or opening a crafted malicious file, making it particularly insidious as it leverages social engineering tactics to achieve exploitation.
The technical implementation of this vulnerability occurs within the PDF processing engine of Foxit Reader where AcroForm fields are handled. When a malicious PDF document contains specially crafted Field objects with malformed richValue properties, the application fails to validate whether the underlying object reference exists before attempting to access or manipulate it. This improper validation creates a scenario where the application may attempt to dereference a null or invalid pointer, potentially leading to memory disclosure or other exploitable conditions. The vulnerability is particularly concerning because it can be leveraged as a stepping stone for more sophisticated attacks, as noted in the ZDI-CAN-8272 reference which indicates this flaw could be combined with other vulnerabilities to achieve code execution. The attack chain typically involves initial information disclosure followed by privilege escalation or code execution within the application context, making it a significant threat to user security.
The operational impact of CVE-2019-6773 extends beyond simple information disclosure, as it creates potential pathways for complete system compromise. Organizations utilizing Foxit Reader for document processing are at risk of unauthorized access to sensitive data, including but not limited to document contents, user information, and potentially system memory contents. The requirement for user interaction makes this vulnerability particularly challenging to defend against through network-level controls alone, as it necessitates endpoint protection and user education. This vulnerability aligns with ATT&CK technique T1059 which covers command and scripting interpreter, as exploitation could potentially lead to execution of arbitrary commands within the application's security context. The attack surface is particularly wide given that Foxit Reader is commonly used for processing PDF documents in enterprise environments, making it a prime target for advanced persistent threat actors seeking to establish footholds within organizational networks.
Mitigation strategies for CVE-2019-6773 should encompass multiple layers of protection including immediate patch deployment from Foxit Corporation, which would address the underlying validation issues in the AcroForm processing engine. Network administrators should implement strict content filtering measures to prevent access to suspicious PDF documents and consider sandboxing PDF processing activities to limit potential damage. Endpoint protection solutions should be configured to monitor for unusual file access patterns and memory operations that may indicate exploitation attempts. Organizations should also consider implementing user awareness training programs to reduce the likelihood of successful social engineering attacks that could lead to exploitation. Additionally, the principle of least privilege should be enforced by ensuring that Foxit Reader operates with minimal necessary permissions and that document processing occurs in restricted environments. Regular security assessments and vulnerability scanning should be conducted to identify similar validation flaws in other PDF processing applications and ensure comprehensive protection against similar attack vectors.