CVE-2015-8559 in Chef Infra Client
Summary
by MITRE
The knife bootstrap command in chef leaks the validator.pem private RSA key to /var/log/messages.
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Analysis
by VulDB Data Team • 07/13/2026
The vulnerability involves a critical security flaw in Chef's knife bootstrap command where the validator.pem private RSA key is inadvertently written to the system log file at /var/log/messages. This represents a severe privilege escalation and credential exposure issue that undermines the fundamental security model of chef infrastructure management. The leak occurs during the bootstrap process when the system attempts to establish initial connectivity with the chef server, and the private key material becomes accessible through logging mechanisms that are not properly secured or sanitized.
This technical flaw stems from improper input validation and output handling within the knife command implementation, where sensitive cryptographic material is passed through logging functions without proper sanitization. The vulnerability directly maps to CWE-209 Information Exposure Through an Error Message, as the private key is exposed through system logging rather than being properly secured or encrypted during processing. The issue also aligns with CWE-312 Cleartext Storage of Sensitive Information in Log Files, since the private key material remains in cleartext within the system logs where it can be accessed by unauthorized users with read permissions.
The operational impact of this vulnerability is profound and far-reaching across enterprise infrastructure security. An attacker who gains access to the system logs or has privileges to read /var/log/messages can immediately extract the validator.pem private key, which grants full administrative access to the chef server and all managed nodes within that infrastructure. This allows for complete compromise of the configuration management system, enabling unauthorized modifications to node configurations, deployment of malicious code, and potential lateral movement throughout the network. The exposure of this key essentially removes the authentication boundary that protects the chef server from unauthorized access.
The vulnerability affects organizations using Chef configurations where knife bootstrap commands are executed with administrative privileges, particularly in environments where system logs are not properly secured or monitored for sensitive information exposure. This issue is especially critical in regulated environments where compliance requirements mandate strict control over cryptographic key management and audit trails. The attack surface extends beyond simple log file access to include any scenario where the system administrator's environment may expose these logs through backup processes, monitoring tools, or shared logging infrastructure.
Mitigation strategies should focus on immediate log sanitization of sensitive data during bootstrap operations, implementing proper secure logging mechanisms that prevent credential exposure, and establishing strict access controls over system log files. Organizations must configure their logging infrastructure to filter out cryptographic key material before writing to persistent storage, implement automated monitoring for sensitive information in logs, and regularly audit system log access permissions. Additionally, the knife bootstrap command should be updated to use secure temporary storage for private keys that are automatically destroyed after successful bootstrap completion. The implementation should follow NIST guidelines for cryptographic key management and ensure that all sensitive information is handled according to security best practices outlined in the ATT&CK framework's credential access and privilege escalation techniques. System administrators should also implement proper log rotation policies with secure deletion of old log entries containing sensitive material and establish automated alerts for potential credential exposure events within their monitoring infrastructure.