CVE-2021-38573 in Foxit
Summary
by MITRE • 08/12/2021
An issue was discovered in Foxit Reader and PhantomPDF before 10.1.4. It allows writing to arbitrary files because a CombineFiles pathname is not validated.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability identified as CVE-2021-38573 affects Foxit Reader and PhantomPDF software versions prior to 10.1.4, representing a critical file system security flaw that enables unauthorized file operations. This issue stems from insufficient validation of file paths during the CombineFiles functionality, creating a pathway for malicious actors to manipulate the software's file handling processes. The vulnerability specifically targets the software's ability to manage multiple PDF files through a combining operation, where the application fails to properly sanitize or validate the pathname parameter provided during this process.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious CombineFiles operation that specifies an arbitrary file path for output. Without proper validation, the software accepts this path and proceeds to write the combined PDF content to the specified location, potentially overwriting critical system files or creating malicious files in sensitive directories. This flaw falls under the category of improper input validation as defined by CWE-20, specifically addressing weaknesses in the validation of pathname parameters within file system operations. The vulnerability creates a path traversal condition that allows attackers to write files outside of intended directories, effectively bypassing normal file system access controls and permissions.
The operational impact of this vulnerability extends beyond simple file manipulation, as it provides attackers with the capability to execute persistent malicious operations within the target system. An attacker could leverage this vulnerability to overwrite system binaries, inject malicious code into PDF processing workflows, or create backdoor files in strategic locations. The implications are particularly severe in enterprise environments where PDF processing is common, as this vulnerability could enable attackers to establish persistent access or disrupt critical document workflows. The attack surface is broad since PDF files are frequently shared and processed in business environments, making this vulnerability particularly dangerous for organizations that rely heavily on document management systems.
Security professionals should implement immediate mitigations including updating to Foxit Reader and PhantomPDF version 10.1.4 or later, which contains the necessary patches to validate CombineFiles pathnames. Organizations should also consider implementing additional security controls such as restricting file system write permissions for PDF processing applications, monitoring for unusual file creation patterns, and conducting regular security assessments of document processing workflows. From an ATT&CK framework perspective, this vulnerability maps to techniques involving file and directory permissions modification and persistence mechanisms, as attackers could use this capability to establish long-term access to systems through malicious file creation. Network segmentation and application whitelisting strategies should also be considered to limit the potential impact of exploitation. The vulnerability highlights the importance of input validation in all file system operations and serves as a reminder of the critical need for proper path validation in applications that handle user-supplied data.