CVE-2017-16764 in django_make_app
Summary
by MITRE
An exploitable vulnerability exists in the YAML parsing functionality in the read_yaml_file method in io_utils.py in django_make_app 0.1.3. A YAML parser can execute arbitrary Python commands resulting in command execution. An attacker can insert Python into loaded YAML to trigger this vulnerability.
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Analysis
by VulDB Data Team • 12/05/2019
The vulnerability identified as CVE-2017-16764 represents a critical security flaw in the django_make_app framework version 0.1.3, specifically within the io_utils.py module where the read_yaml_file method processes YAML data. This issue falls under the category of code injection vulnerabilities and is classified as CWE-94, which encompasses "Improper Control of Generation of Code ('Code Injection')" in the Common Weakness Enumeration catalog. The vulnerability stems from the insecure handling of YAML parsing operations that directly execute Python code without proper sanitization or validation of user-supplied input.
The technical implementation of this flaw occurs when the application processes YAML files through the read_yaml_file function, which utilizes Python's YAML parsing capabilities to deserialize data structures. The vulnerability arises because the YAML parser in this specific implementation does not properly restrict the types of objects that can be created during deserialization, allowing attackers to inject malicious Python code within the YAML payload. This creates a path for arbitrary code execution where an attacker can craft specially formatted YAML content that, when parsed, executes unintended Python commands on the target system. The vulnerability is particularly dangerous because it operates at the parsing level, meaning that any YAML file processed through this method becomes a potential attack vector.
The operational impact of this vulnerability extends beyond simple command execution to encompass full system compromise capabilities. An attacker who can influence the content of YAML files processed by this application can execute arbitrary commands with the privileges of the application itself, potentially leading to complete system takeover. This vulnerability affects any environment where django_make_app 0.1.3 is deployed and processes user-supplied or untrusted YAML content. The attack surface includes scenarios where YAML files might be uploaded by users, fetched from external sources, or generated by the application itself, making the vulnerability particularly concerning for web applications that handle configuration files or data import operations. The vulnerability aligns with ATT&CK technique T1059.001, which covers "Command and Scripting Interpreter: Python" as attackers can leverage this flaw to execute malicious Python code directly on the target system.
Mitigation strategies for CVE-2017-16764 require immediate attention through multiple defensive layers. The most effective immediate solution involves upgrading to a patched version of django_make_app where the YAML parsing functionality has been properly secured to prevent arbitrary code execution. Organizations should implement strict input validation and sanitization measures for all YAML content, particularly when it originates from untrusted sources. The use of safe YAML parsers such as yaml.safe_load() instead of the default loader should be enforced throughout the application. Additionally, implementing proper access controls and least privilege principles can limit the potential damage from successful exploitation. Security monitoring should be enhanced to detect unusual patterns in YAML file processing or unexpected command execution activities. Organizations should also consider implementing network segmentation and application firewalls to limit the attack surface and contain potential breaches. The vulnerability serves as a reminder of the critical importance of secure coding practices and the dangers of using insecure deserialization methods in applications that process external data formats.