CVE-2021-33794 in Foxit
Summary
by MITRE • 08/12/2021
Foxit Reader before 10.1.4 and PhantomPDF before 10.1.4 allow information disclosure or an application crash after mishandling the Tab key during XFA form interaction.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability identified as CVE-2021-33794 represents a critical information disclosure and application stability issue affecting Foxit Reader and PhantomPDF software versions prior to 10.1.4. This flaw manifests during the interaction with XFA forms when the Tab key is processed incorrectly, leading to potentially severe consequences for users and organizations relying on these PDF processing applications. The vulnerability falls under the category of improper input handling and memory management issues that can result in unauthorized data exposure and system instability.
The technical root cause of this vulnerability stems from inadequate validation and handling of keyboard input events within the XFA form processing engine of these PDF readers. When users navigate through form fields using the Tab key, the application fails to properly manage the state transitions and memory allocation associated with these interactions. This improper handling creates conditions where sensitive information stored in memory may be inadvertently exposed or where the application's memory management structures become corrupted, leading to application crashes or unexpected behavior. The flaw specifically impacts the tab navigation functionality within XFA forms, which are XML-based forms used in PDF documents for complex data entry and processing scenarios.
From an operational perspective, this vulnerability presents significant risks to organizations that rely heavily on PDF form processing and document management systems. The information disclosure aspect could potentially expose sensitive data such as personal identification information, financial records, or proprietary business data that users enter into XFA forms. Additionally, the application crash vulnerability means that legitimate document processing activities could be interrupted, causing productivity losses and potential data loss. The vulnerability is particularly concerning because it affects widely used PDF processing software, making it a prime target for exploitation in targeted attacks against organizations that handle sensitive information. Security researchers have categorized this issue as a memory corruption vulnerability that could be leveraged for more sophisticated attacks.
Organizations should immediately update to Foxit Reader version 10.1.4 or later and PhantomPDF version 10.1.4 or later to remediate this vulnerability. The update process should be prioritized across all systems where these applications are installed, particularly in environments handling sensitive data or critical business processes. System administrators should also implement monitoring for any unusual application behavior or crashes that might indicate exploitation attempts. Additionally, organizations should consider implementing network-based controls and application whitelisting measures to limit the attack surface and prevent unauthorized execution of vulnerable versions. This vulnerability aligns with several ATT&CK techniques including T1059 for command and scripting interpreter usage and T1203 for exploitation for privilege escalation, as it could potentially be used as a foothold for more extensive attacks. The CWE mapping for this issue would be CWE-125 for out-of-bounds read and CWE-20 for improper input validation, highlighting the dual nature of the vulnerability as both a memory access issue and input handling flaw.