CVE-2019-6772 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on vulnerable installations of Foxit Reader 2019.010.20098. 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 removeField method when processing 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-8231.
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Analysis
by VulDB Data Team • 09/26/2023
The vulnerability identified as CVE-2019-6772 represents a critical information disclosure flaw affecting Foxit Reader version 2019.010.20098 and potentially other versions within the same release cycle. This security weakness resides within the application's handling of AcroForm fields, specifically within the removeField method implementation. The flaw demonstrates a classic object validation error that occurs when the software fails to verify whether an object exists before attempting operations on it. This particular vulnerability type aligns with CWE-476 which defines NULL Pointer Dereference as a common software security weakness where programs attempt to access memory locations through null pointers. The vulnerability requires user interaction to be exploited effectively, meaning that an attacker must convince a target to visit a malicious web page or open a specially crafted malicious PDF file containing the vulnerable code.
The technical exploitation of this vulnerability occurs when Foxit Reader processes AcroForm elements within PDF documents, particularly during the removal of form fields. When the removeField method executes without proper validation of object existence, it creates a scenario where memory operations can be performed on invalid or null references. This condition allows attackers to manipulate the application's memory state in ways that can reveal sensitive information stored in memory locations that should remain protected. The vulnerability's impact extends beyond simple information disclosure, as it can be leveraged as a stepping stone for more sophisticated attacks. According to ATT&CK framework, this vulnerability maps to T1059.007 which describes Windows Command Shell usage, and potentially T1068 which covers Exploitation for Privilege Escalation. The lack of proper input validation creates a path for attackers to potentially execute arbitrary code within the context of the current process, effectively elevating their privileges to match those of the Foxit Reader application itself.
The operational impact of CVE-2019-6772 extends significantly beyond the immediate information disclosure threat, as it provides attackers with a foundation for more comprehensive attacks against systems running vulnerable versions of Foxit Reader. Organizations that deploy Foxit Reader for document processing, especially in environments where users frequently open PDF documents from external sources, face substantial risk from this vulnerability. The attack surface becomes particularly large when considering that PDF documents can be distributed through various channels including email attachments, web downloads, and file sharing platforms. The vulnerability's exploitation requires user interaction, but this requirement does not significantly reduce the risk level, as social engineering tactics can effectively bypass user awareness and security measures. Security professionals should consider this vulnerability in the context of broader attack chains where it can serve as an initial compromise vector leading to full system compromise. The vulnerability's classification as a remote attack vector means that attackers can exploit it without requiring physical access to target systems, making it particularly dangerous in enterprise environments where users may inadvertently encounter malicious PDF content.
Mitigation strategies for CVE-2019-6772 should focus on both immediate remediation and long-term security enhancements. The primary recommendation involves updating to the latest version of Foxit Reader where the vulnerability has been patched, as this directly addresses the root cause of the issue. Organizations should implement strict document filtering policies that prevent users from opening PDF files from untrusted sources, particularly when these documents contain complex AcroForm elements. Network-level controls such as web application firewalls and content filtering solutions should be configured to block access to known malicious PDF hosting sites and to scan incoming PDF content for suspicious elements. Security teams should also consider implementing user education programs that emphasize the dangers of opening PDF documents from unknown sources and the importance of verifying document authenticity. The vulnerability highlights the importance of proper input validation and object existence checks in software development, and organizations should review their development practices to ensure similar flaws do not exist in other applications. Additionally, system monitoring should be enhanced to detect unusual memory access patterns that might indicate exploitation attempts, and incident response procedures should be updated to include specific handling protocols for this vulnerability type.