CVE-2017-16763 in Confire
Summary
by MITRE
An exploitable vulnerability exists in the YAML parsing functionality in config.py in Confire 0.2.0. Due to the user-specific configuration being loaded from "~/.confire.yaml" using the yaml.load function, 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 • 01/10/2023
The vulnerability identified as CVE-2017-16763 represents a critical security flaw in the Confire 0.2.0 configuration management library that directly enables remote code execution through improper input validation. This issue stems from the application's reliance on the yaml.load function when processing user-specific configuration files stored in the standard Unix home directory at "~/.confire.yaml". The fundamental problem lies in how the YAML parser handles untrusted input, creating an environment where maliciously crafted configuration data can be interpreted as executable Python code rather than simple data structures.
The technical exploitation of this vulnerability occurs through the inherent behavior of Python's yaml.load function which does not sanitize input and can execute arbitrary Python objects during parsing. When an attacker crafts a malicious YAML file containing Python code within the configuration structure, the yaml.load function processes these objects and executes them within the application context. This creates a direct code execution vector that allows attackers to run arbitrary commands on the system where the vulnerable application is running. The vulnerability is classified as a command injection flaw that leverages the YAML deserialization process to achieve arbitrary code execution, making it particularly dangerous for applications that rely on user-provided configuration data.
The operational impact of this vulnerability extends beyond simple privilege escalation as it allows attackers to gain complete control over the affected system. Since the configuration file is loaded from the user's home directory, any user with write access to their own configuration can potentially exploit this vulnerability. The attack surface is broadened because the vulnerability exists in the parsing logic rather than in specific user input handling, meaning that any application using Confire 0.2.0 for configuration management is at risk. This type of vulnerability falls under CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and aligns with ATT&CK technique T1059.001 for command and scripting interpreter execution.
Mitigation strategies for this vulnerability require immediate remediation through the use of safe YAML loading practices. The primary fix involves replacing yaml.load with yaml.safe_load throughout the application codebase to prevent execution of arbitrary Python objects. Additionally, applications should implement proper input validation and sanitization for all configuration files, ensuring that user-provided data undergoes strict verification before processing. System administrators should also consider implementing file access controls and monitoring for unauthorized modifications to configuration files in user home directories. The vulnerability demonstrates the critical importance of avoiding unsafe deserialization patterns and implementing proper security controls when handling user-provided data in configuration management systems.