CVE-2021-38570 in PhantomPDF
Summary
by MITRE • 08/12/2021
An issue was discovered in Foxit Reader and PhantomPDF before 10.1.4. It allows attackers to delete arbitrary files (during uninstallation) via a symlink.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability identified as CVE-2021-38570 represents a critical privilege escalation and arbitrary file deletion flaw affecting Foxit Reader and PhantomPDF versions prior to 10.1.4. This issue stems from improper handling of symbolic links during the uninstallation process, creating a significant attack vector for malicious actors who can leverage this weakness to execute unauthorized file operations on affected systems.
The technical implementation of this vulnerability occurs within the uninstallation routine of these PDF reading applications where symbolic link resolution is not properly validated or sanitized. When the uninstaller processes certain file paths, it fails to verify whether the target represents a legitimate file or a symbolic link pointing to a different location. This weakness allows attackers to craft malicious symlink structures that, when processed during uninstallation, cause the system to delete files at arbitrary locations within the filesystem rather than just the intended application files.
From an operational perspective, this vulnerability poses severe risks to enterprise environments where these applications are commonly deployed. Attackers can exploit this flaw to remove critical system files, configuration data, or even security tools that might be protecting the compromised system. The impact extends beyond simple file deletion as it can be leveraged to disrupt system operations, create backdoor access points, or facilitate further attacks through the removal of security controls. The vulnerability is particularly dangerous because it operates at the system level during uninstallation, a process that typically requires elevated privileges and is often overlooked during security assessments.
The attack surface for this vulnerability is significant given the widespread deployment of Foxit Reader and PhantomPDF across various organizations. The flaw aligns with CWE-59, which describes improper handling of symbolic links, and demonstrates characteristics consistent with privilege escalation techniques documented in the MITRE ATT&CK framework under T1068 for locally executed code and T1059 for command and scripting interpreter usage. Organizations running affected versions of these applications face potential compromise scenarios where attackers can manipulate the uninstallation process to achieve persistent access or system disruption.
Mitigation strategies should prioritize immediate patching of affected applications to version 10.1.4 or later, which contains the necessary fixes for proper symlink handling during uninstallation. Additionally, system administrators should implement strict access controls and monitoring around uninstallation processes, particularly for applications with elevated privileges. Network segmentation and application whitelisting policies can help limit the potential impact of exploitation attempts. Regular security assessments should include verification of uninstallation procedures and proper handling of symbolic links to prevent similar vulnerabilities from being introduced in other software components.