CVE-2018-17671 in Foxit
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on vulnerable installations of Foxit Reader 9.2.0.9297. 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 Lower method of a XFA object. The issue results from the lack of proper validation of user-supplied data, which can result in a read past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-6617.
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Analysis
by VulDB Data Team • 05/05/2020
CVE-2018-17671 represents a critical buffer over-read vulnerability affecting Foxit Reader version 9.2.0.9297 that demonstrates a classic weakness in input validation and memory management practices within PDF processing applications. This vulnerability operates through the XFA (XML Forms Architecture) object handling mechanism, specifically targeting the Lower method implementation where insufficient bounds checking allows malicious input to traverse memory boundaries beyond allocated buffer limits. The vulnerability resides in the fundamental security principle of validating all user-supplied data before processing, which directly correlates to CWE-125, known as "Out-of-Bounds Read" and represents a common attack vector exploited by adversaries seeking to gain unauthorized access to system resources.
The exploitation scenario requires user interaction through either visiting a malicious webpage or opening a crafted PDF file that contains specially constructed XFA objects designed to trigger the vulnerable Lower method. This user interaction requirement places the vulnerability in the category of client-side attacks that typically leverage social engineering techniques to deliver malicious payloads. The operational impact extends beyond simple information disclosure to include potential code execution within the context of the currently running Foxit Reader process, making it particularly dangerous for enterprise environments where PDF processing is common. The vulnerability's classification as a remote code execution threat aligns with ATT&CK technique T1203, "Exploitation for Client Execution," which describes how adversaries can leverage application vulnerabilities to execute malicious code on target systems.
The technical flaw stems from inadequate memory boundary validation within the XFA processing subsystem, where the application fails to properly verify that user-provided data remains within expected buffer limits during the Lower method operation. This oversight creates a predictable attack surface that adversaries can exploit by crafting malicious XFA structures that cause the application to read memory locations beyond the intended buffer boundaries. The vulnerability's potential for code execution arises because the buffer over-read can be manipulated to access and potentially corrupt memory regions that contain executable code or control structures, enabling attackers to inject and execute arbitrary code with the privileges of the Foxit Reader process. This represents a significant security risk in environments where PDF documents are frequently opened from untrusted sources, as the vulnerability can be triggered through simple document viewing operations.
Organizations should prioritize immediate patch deployment for this vulnerability as it represents a high-risk exposure that can be exploited without requiring advanced technical skills from adversaries. The mitigation strategy should include implementing strict document validation policies, deploying web application firewalls to filter malicious PDF content, and establishing user education programs to reduce successful social engineering campaigns. Security teams should also monitor for indicators of compromise related to this vulnerability, including unusual network connections from Foxit Reader processes and anomalous memory access patterns that might indicate exploitation attempts. The vulnerability's presence in a widely used PDF reader application underscores the importance of maintaining up-to-date security patches and implementing layered defense strategies that can protect against both known and emerging threats in the document processing ecosystem.