CVE-2009-3274 in Firefox
Summary
by MITRE
Mozilla Firefox 3.6a1, 3.5.3, 3.5.2, and earlier 3.5.x versions, and 3.0.14 and earlier 2.x and 3.x versions, on Linux uses a predictable /tmp pathname for files selected from the Downloads window, which allows local users to replace an arbitrary downloaded file by placing a file in a /tmp location before the download occurs, related to the Download Manager component. NOTE: some of these details are obtained from third party information.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/23/2021
This vulnerability resides in the Download Manager component of Mozilla Firefox versions prior to 3.6a1, 3.5.3, 3.0.14, and their respective earlier releases across both 2.x and 3.x series on Linux systems. The core issue stems from the predictable naming convention used for temporary files within the /tmp directory during download operations. When users initiate downloads through the Firefox interface, the application creates temporary files using hardcoded or easily guessable pathnames that do not incorporate sufficient entropy or randomization mechanisms. This predictable file naming behavior creates a window of opportunity for local privilege escalation attacks where malicious users can exploit the timing gap between when Firefox prepares the temporary file and when it completes the download process.
The technical flaw manifests as a race condition vulnerability where an attacker can create a symbolic link or replace a legitimate file in the /tmp directory with their own malicious content before Firefox finishes writing to the temporary location. This vulnerability is classified under CWE-377 as "Insecure Temporary File" and relates to CWE-367 which addresses "Time-of-Check to Time-of-Use (TOCTOU) Race Conditions." The flaw specifically impacts the Download Manager component by leveraging the predictable nature of temporary file creation, allowing attackers to manipulate the download destination and potentially execute arbitrary code or gain unauthorized access to system resources. This weakness enables attackers to substitute legitimate downloaded files with malicious counterparts, potentially leading to privilege escalation or data compromise.
The operational impact of this vulnerability is significant for Linux environments where Firefox is commonly used as a web browser. Attackers can exploit this weakness to replace critical system files, configuration files, or user data with malicious alternatives, potentially leading to complete system compromise. The vulnerability affects not only individual user sessions but also enterprise environments where multiple users may be running vulnerable Firefox versions. The attack vector requires local system access but does not need network connectivity to the target system, making it particularly dangerous in scenarios where local privilege escalation is possible. This weakness can be exploited by any local user with access to the system, potentially allowing for privilege escalation attacks where attackers can gain elevated privileges to execute malicious code with higher system permissions.
Mitigation strategies should focus on immediate patching of affected Firefox versions to the latest stable releases that address the predictable temporary file naming issue. System administrators should implement proper file permissions and access controls on /tmp directories to limit the ability of unauthorized users to create or modify files in these locations. Additionally, organizations should consider implementing monitoring solutions that can detect suspicious file creation patterns in temporary directories. The vulnerability demonstrates the importance of proper temporary file handling in software development, emphasizing the need for using secure randomization techniques and avoiding predictable pathnames in sensitive operations. Security hardening measures such as setting the TMPDIR environment variable to non-standard locations with restricted permissions can provide additional layers of protection against such attacks, aligning with the principles of defense in depth and secure coding practices.