CVE-2019-9798 in Firefox
Summary
by MITRE
On Android systems, Firefox can load a library from APITRACE_LIB, which is writable by all users and applications. This could allow malicious third party applications to execute a man-in-the-middle attack if a malicious code was written to that location and loaded. *Note: This issue only affects Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 66.
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Analysis
by VulDB Data Team • 09/07/2023
The vulnerability described in CVE-2019-9798 represents a critical privilege escalation and man-in-the-middle attack vector specific to Android implementations of Firefox. This flaw stems from Firefox's improper handling of library loading mechanisms on Android systems, where the application fails to properly validate or restrict access to the APITRACE_LIB environment variable. The vulnerability exists because this specific library path is configured with permissive permissions that allow any application or user to write to it, creating a dangerous attack surface where malicious actors can manipulate the system's library loading behavior.
The technical implementation of this vulnerability exploits the fundamental principle of dynamic library loading in Android environments. When Firefox initializes on Android systems, it attempts to load libraries from the APITRACE_LIB path without proper security checks or validation of the library's integrity. This creates a path traversal and code injection vulnerability where an attacker can place a malicious shared library at this location, which will then be loaded by Firefox during execution. The flaw directly relates to CWE-427 Uncontrolled Search Path Element, where the application's search path is not properly controlled, allowing attackers to inject malicious code through the specified library path.
From an operational perspective, this vulnerability enables sophisticated attack scenarios that can compromise user data and system integrity. An attacker with access to write permissions on the APITRACE_LIB path can craft a malicious library that mimics legitimate system functions or network components, effectively allowing them to intercept and manipulate network traffic or system calls made by Firefox. This creates a persistent man-in-the-middle attack capability that can be maintained across system reboots and Firefox sessions. The vulnerability also aligns with ATT&CK technique T1059 Command and Scripting Interpreter, as it allows for the execution of arbitrary code through library injection mechanisms.
The impact of this vulnerability extends beyond simple code execution to include potential data theft, session hijacking, and network monitoring capabilities. Since Firefox is a widely used web browser that handles sensitive user information, an attacker could intercept HTTPS traffic, capture login credentials, or redirect users to malicious websites. The attack requires only local write access to the specific library path, making it particularly dangerous as it can be exploited by any application installed on the device. This vulnerability also demonstrates the importance of secure library loading practices and proper privilege separation in mobile application development. The fact that this affects only Android systems highlights the unique security challenges present in mobile environments where multiple applications share the same file system with potentially permissive access controls. Organizations should implement immediate mitigations including updating to Firefox version 66 or later, where this vulnerability has been addressed, and conducting security audits of library loading mechanisms in other applications that may exhibit similar behaviors.