CVE-2016-8856 in Foxit
Summary
by MITRE
Foxit Reader for Mac 2.1.0.0804 and earlier and Foxit Reader for Linux 2.1.0.0805 and earlier suffered from a vulnerability where weak file permissions could be exploited by attackers to execute arbitrary code. After the installation, Foxit Reader's core files were world-writable by default, allowing an attacker to overwrite them with backdoor code, which when executed by privileged user would result in Privilege Escalation, Code Execution, or both.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2016-8856 represents a critical security flaw in Foxit Reader versions for both macOS and Linux platforms. This weakness stems from improper file permission configuration during the installation process, creating a fundamental breach in the software's security model. The issue affects Foxit Reader for Mac versions 2.1.0.0804 and earlier, as well as Foxit Reader for Linux versions 2.1.0.0805 and earlier, indicating a widespread problem across multiple operating systems. The vulnerability is categorized under CWE-732, which specifically addresses Incorrect Permission Assignment for Critical Resources, making it a clear example of improper access control mechanisms.
The technical exploitation of this vulnerability relies on the fundamental principle of privilege escalation through file system manipulation. During normal installation procedures, Foxit Reader's core executable files are configured with world-writable permissions, meaning any user account on the system can modify these critical components. This misconfiguration creates a persistent attack vector where malicious actors can replace legitimate executable files with malicious payloads without requiring elevated privileges initially. The flaw operates at the system-level file permissions model, where the default installation process fails to enforce proper access controls that should restrict write permissions to only authorized system administrators or the software installation process itself.
The operational impact of CVE-2016-8856 extends beyond simple code execution to encompass complete system compromise through privilege escalation. When a user with standard privileges installs or runs the vulnerable Foxit Reader application, they inadvertently create a situation where any attacker can modify core application files. Once modified, these files execute with the privileges of the user who runs them, which typically includes elevated permissions when the application is launched by privileged users. This creates a scenario where a local attacker can gain system-level control through a simple file overwrite operation, effectively bypassing traditional security boundaries and access controls that should protect system integrity.
The exploitation chain for this vulnerability follows a predictable pattern that aligns with ATT&CK technique T1068, which covers 'Local Privilege Escalation'. Attackers first need to gain access to a system where the vulnerable software is installed, typically through social engineering, phishing, or other initial compromise methods. Once they have a foothold, they can leverage the weak file permissions to replace legitimate executable files with malicious versions. The subsequent execution of these modified files by legitimate users or system processes results in code execution with elevated privileges, potentially enabling full system compromise. This vulnerability demonstrates how seemingly minor configuration issues can create significant security risks when combined with common user behaviors and system access patterns.
Mitigation strategies for CVE-2016-8856 require immediate attention through proper file permission management and system hardening practices. The most effective immediate solution involves manually correcting file permissions after installation by setting restrictive access controls that prevent unauthorized modification of core application files. System administrators should implement automated checks to verify proper file permissions and ensure that critical application components maintain appropriate ownership and access restrictions. The remediation process should include running permission audits and implementing security policies that enforce proper access control mechanisms during software installation. Organizations should also consider implementing application whitelisting solutions that can prevent execution of unauthorized modifications to critical system files, providing an additional layer of defense against similar vulnerabilities that may exist in other software applications.