CVE-2017-9450 in AWS CloudFormation Bootstrap Tools
Summary
by MITRE
The Amazon Web Services (AWS) CloudFormation bootstrap tools package (aka aws-cfn-bootstrap) before 1.4-19.10 allows local users to execute arbitrary code with root privileges by leveraging the ability to create files in an unspecified directory.
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Analysis
by VulDB Data Team • 12/02/2019
The vulnerability identified as CVE-2017-9450 affects the AWS CloudFormation bootstrap tools package, specifically versions prior to 1.4-19.10, creating a critical privilege escalation risk within AWS cloud environments. This flaw resides in the package's handling of file creation operations within an unspecified directory, which malicious local users can exploit to execute arbitrary code with root privileges. The issue represents a significant security weakness because CloudFormation bootstrap tools are commonly used during instance initialization and system configuration processes, making them prime targets for attackers seeking persistent access to cloud infrastructure. The vulnerability's impact extends beyond simple local privilege escalation as it directly undermines the security model of AWS instances that rely on these bootstrap tools for proper system initialization and configuration.
The technical flaw stems from insufficient directory permissions and inadequate file creation validation within the aws-cfn-bootstrap package implementation. When the bootstrap tools execute during cloud instance provisioning, they create temporary files and configuration artifacts in a directory that lacks proper access controls. This directory allows local users to create files with elevated privileges, effectively enabling privilege escalation attacks. The vulnerability aligns with CWE-276, which describes improper file permissions, and CWE-78, which addresses OS command injection vulnerabilities. Attackers can leverage this weakness by placing malicious files in the vulnerable directory, which then get executed with root privileges during subsequent bootstrap operations. The exploit requires local access to the system but provides complete root compromise, making it particularly dangerous in multi-tenant cloud environments where isolation is critical.
The operational impact of this vulnerability is severe for organizations relying on AWS CloudFormation for infrastructure automation, as it can lead to complete system compromise and potential data breaches. Cloud instances that utilize the affected bootstrap tools become vulnerable to persistent attacks where attackers can establish backdoors, exfiltrate data, or use compromised systems as launching points for further attacks within the AWS environment. This vulnerability particularly affects organizations using automated provisioning workflows, as the bootstrap process often runs with elevated privileges to configure system settings, network parameters, and security configurations. The attack vector is particularly concerning because it operates at the system level rather than application level, meaning that successful exploitation can bypass many traditional application security controls and monitoring mechanisms.
Mitigation strategies should focus on immediate package updates to version 1.4-19.10 or later, which addresses the directory permission issues and implements proper file creation validation. Organizations should also implement additional security controls such as restricting local user access to cloud instances, monitoring file creation activities in sensitive directories, and implementing principle of least privilege for bootstrap tool operations. The remediation process should include comprehensive vulnerability scanning across all AWS instances using affected bootstrap tools, followed by immediate patch deployment and configuration validation. Security teams should also consider implementing runtime monitoring for suspicious file creation patterns and privilege escalation attempts, as outlined in the MITRE ATT&CK framework under techniques related to privilege escalation and persistence. Additionally, organizations should review their CloudFormation templates and bootstrap configurations to ensure that unnecessary elevated privileges are not granted during system initialization processes, reducing the attack surface for similar vulnerabilities.