CVE-2017-16618 in OwlMixin
Summary
by MITRE
An exploitable vulnerability exists in the YAML loading functionality of util.py in OwlMixin before 2.0.0a12. A "Load YAML" string or file (aka load_yaml or load_yamlf) can execute arbitrary Python commands resulting in command execution because load is used where safe_load should have been used. An attacker can insert Python into loaded YAML to trigger this vulnerability.
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Analysis
by VulDB Data Team • 01/06/2023
The vulnerability identified as CVE-2017-16618 represents a critical security flaw in the YAML loading implementation of OwlMixin utility library prior to version 2.0.0a12. This issue stems from the improper use of Python's yaml.load() function instead of the safer yaml.safe_load() function within the util.py module. The flaw creates a remote code execution vector that allows attackers to inject and execute arbitrary Python commands through maliciously crafted YAML input. The vulnerability specifically affects the load_yaml and load_yamlf functions which are designed to process YAML formatted data, making them susceptible to code injection attacks that can compromise the entire system.
The technical root cause of this vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and is particularly relevant to the improper use of untrusted data in YAML parsing operations. When the yaml.load() function processes input data, it deserializes Python objects directly from the YAML stream, including complex data structures that can contain executable code. In contrast, yaml.safe_load() only processes basic YAML data types and prevents the execution of arbitrary Python code. The flaw enables attackers to construct YAML payloads containing Python object constructors, which get executed during the deserialization process, resulting in complete system compromise. This type of vulnerability is classified under the MITRE ATT&CK framework as a code injection technique, specifically targeting the execution of arbitrary commands through deserialization vulnerabilities.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with full control over the affected system. An attacker who can influence the YAML input processed by the vulnerable functions can execute arbitrary system commands, potentially leading to data exfiltration, privilege escalation, or further network infiltration. The vulnerability is particularly dangerous because it can be exploited through various attack vectors including file uploads, configuration file manipulation, or any scenario where untrusted YAML data is processed. The lack of proper input validation and sanitization in the YAML loading functions creates a persistent threat that can affect any application using the vulnerable OwlMixin library. Organizations utilizing this library are at risk of complete system compromise, as the vulnerability allows for the execution of malicious payloads without requiring additional privileges or complex exploitation techniques.
Mitigation strategies for CVE-2017-16618 focus on immediate remediation through library updates and implementation of secure coding practices. The primary fix involves upgrading to OwlMixin version 2.0.0a12 or later, which addresses the vulnerability by replacing yaml.load() with yaml.safe_load() throughout the utility functions. Additionally, organizations should implement input validation and sanitization measures to prevent untrusted data from reaching the YAML parsing functions. Security teams should conduct comprehensive code reviews to identify all instances where yaml.load() might be used in similar contexts, ensuring that safe_load() is consistently employed for untrusted input. Network segmentation and monitoring should be implemented to detect potential exploitation attempts, while application-level firewalls can be configured to filter suspicious YAML content. The vulnerability serves as a critical reminder of the importance of using safe deserialization functions and following secure coding guidelines to prevent code injection attacks that can lead to complete system compromise.