CVE-2014-1402 in Jinja2
Summary
by MITRE
The default configuration for bccache.FileSystemBytecodeCache in Jinja2 before 2.7.2 does not properly create temporary files, which allows local users to gain privileges via a crafted .cache file with a name starting with __jinja2_ in /tmp.
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Analysis
by VulDB Data Team • 03/21/2022
The vulnerability identified as CVE-2014-1402 affects the Jinja2 template engine version 2.7.1 and earlier, specifically targeting the default configuration of the bccache.FileSystemBytecodeCache component. This flaw represents a privilege escalation vulnerability that arises from improper handling of temporary file creation within the /tmp directory. The issue stems from the insecure creation of temporary files during bytecode caching operations, which creates opportunities for local attackers to manipulate the system's privilege structure through carefully crafted malicious cache files.
The technical implementation of this vulnerability exploits a race condition and insecure temporary file creation pattern within the Jinja2 caching mechanism. When the FileSystemBytecodeCache component generates temporary files, it creates them in the /tmp directory without proper security measures to prevent symlink attacks or file replacement attacks. An attacker can create a malicious .cache file with a filename starting with _jinja2 in the /tmp directory, which the vulnerable Jinja2 application will subsequently process, leading to privilege escalation. This vulnerability directly maps to CWE-377, which addresses insecure temporary file creation, and CWE-276, which covers incorrect permissions for created files.
The operational impact of CVE-2014-1402 is significant for systems running vulnerable versions of Jinja2, particularly in environments where applications may be running with elevated privileges or where multiple users share the same system. The vulnerability allows local users to potentially escalate their privileges to the level of the process running the vulnerable application, which could include system-level privileges depending on how the application is configured. This risk is particularly concerning in web server environments where Jinja2 is commonly used for template rendering, as it could enable attackers to gain unauthorized access to system resources or escalate their access level within the application's security boundaries.
The attack vector for this vulnerability requires local system access and involves the attacker creating a malicious cache file in the /tmp directory before the vulnerable application processes it. The attack is classified under the MITRE ATT&CK framework as privilege escalation through exploitation of insecure temporary file handling, specifically mapping to technique T1068. Organizations should implement immediate mitigations including upgrading to Jinja2 version 2.7.2 or later, which addresses this vulnerability through proper temporary file creation and validation mechanisms. Additional defensive measures include restricting write access to the /tmp directory for non-root users, implementing proper file permission controls, and monitoring for suspicious cache file creation patterns. The vulnerability demonstrates the importance of secure coding practices in temporary file handling and the potential for seemingly minor configuration issues to create significant security risks in application frameworks.