CVE-2017-16576 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Foxit Reader 8.3.1.21155. 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 XFA's field element. 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 under the context of the current process. Was ZDI-CAN-5092.
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Analysis
by VulDB Data Team • 12/16/2019
This vulnerability in Foxit Reader 8.3.1.21155 represents a critical remote code execution flaw that demonstrates poor input validation practices in the XFA (XML Forms Architecture) field element processing. The vulnerability arises from a fundamental lack of object existence validation before operations are performed on potentially uninitialized or invalid objects within the XFA parsing mechanism. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereferences and improper object validation, making it particularly dangerous as it can be exploited through web-based attacks without requiring local system access.
The technical implementation of this vulnerability occurs within the XFA field element handling code where the application fails to verify that referenced objects exist before attempting to manipulate them. When a maliciously crafted PDF document containing specially constructed XFA fields is processed, the application's failure to validate object existence creates a condition where memory corruption can occur, leading to arbitrary code execution. This flaw operates at the application layer and can be triggered through both web page visits and direct file opening, making it particularly versatile for attack vectors. The vulnerability is classified as a remote code execution issue because an attacker can deliver malicious content through web browsers or email attachments without requiring physical access to the target system.
The operational impact of this vulnerability extends beyond simple code execution, as it allows attackers to operate within the security context of the currently running Foxit Reader process. This means that successful exploitation could result in full system compromise, data exfiltration, or further lateral movement within a network. The requirement for user interaction through visiting malicious pages or opening malicious files makes this vulnerability particularly concerning in enterprise environments where users may encounter phishing emails or browse untrusted websites. Attackers can leverage this vulnerability as part of broader attack chains, potentially using it as a foothold for more sophisticated attacks that align with ATT&CK technique T1203 for legitimate credentials and T1059 for command and scripting interpreter execution.
Mitigation strategies for this vulnerability should focus on immediate remediation through official patches provided by Foxit Corporation, as well as network-level defenses such as web application firewalls and content filtering solutions. Organizations should implement strict email filtering and web browsing policies to prevent users from accessing potentially malicious content. Additionally, the principle of least privilege should be enforced by running Foxit Reader with reduced privileges and implementing sandboxing techniques to limit the potential impact of successful exploitation. Security monitoring should be enhanced to detect unusual process behavior or memory access patterns that might indicate exploitation attempts, while regular security assessments should be conducted to identify similar validation flaws in other applications. The vulnerability serves as a reminder of the critical importance of input validation and object lifecycle management in preventing remote code execution attacks that can be triggered through seemingly benign user interactions.