CVE-2011-4953 in cobbler
Summary
by MITRE
The set_mgmt_parameters function in item.py in cobbler before 2.2.2 allows context-dependent attackers to execute arbitrary code via vectors related to the use of the yaml.load function instead of the yaml.safe_load function, as demonstrated using Puppet.
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Analysis
by VulDB Data Team • 04/03/2022
The vulnerability identified as CVE-2011-4953 represents a critical security flaw in the cobbler provisioning system that affects versions prior to 2.2.2. This issue resides within the set_mgmt_parameters function in the item.py module, where the application improperly handles YAML data processing. The vulnerability stems from the application's use of yaml.load instead of the safer yaml.safe_load function, creating an exploitable condition that allows remote attackers to execute arbitrary code on affected systems. The flaw is particularly concerning because it operates in a context-dependent manner, requiring specific conditions to be met for exploitation to occur, making it more subtle and potentially harder to detect during routine security assessments.
The technical implementation of this vulnerability exploits the fundamental differences between yaml.load and yaml.safe_load functions in Python's PyYAML library. The yaml.load function can execute arbitrary Python objects during deserialization, while yaml.safe_load restricts this behavior to only basic YAML tags. When cobbler processes management parameters through the set_mgmt_parameters function, it accepts YAML input that gets processed using the unsafe yaml.load method. An attacker can craft malicious YAML data containing Python objects or code that gets executed during the deserialization process, effectively allowing remote code execution. This type of vulnerability falls under CWE-502, which specifically addresses Deserialization of Untrusted Data, and represents a classic example of insecure deserialization that enables arbitrary code execution through crafted input.
The operational impact of CVE-2011-4953 extends beyond simple remote code execution to encompass potential system compromise and privilege escalation within environments where cobbler is deployed. Since cobbler is commonly used for automated operating system provisioning and configuration management, attackers who successfully exploit this vulnerability can gain control over the provisioning infrastructure itself. This creates a significant risk for organizations that rely on cobbler for managing large-scale deployments, as the compromised system could be used to provision malicious configurations, access sensitive data, or serve as a pivot point for attacking other systems within the network. The vulnerability's context-dependent nature means that exploitation typically requires the attacker to have some level of access to the cobbler management interface or the ability to inject malicious YAML data into the system, making it particularly dangerous in environments where cobbler is exposed to untrusted users or external networks.
Organizations should implement immediate mitigations including upgrading to cobbler version 2.2.2 or later, which contains the necessary patches to address this vulnerability. Additionally, administrators should review and restrict access to cobbler management interfaces, implement proper input validation for YAML data, and consider disabling or restricting the use of yaml.load in favor of yaml.safe_load throughout the application. The remediation efforts should also include monitoring for suspicious activity related to management parameter changes and implementing network segmentation to limit access to cobbler systems. From a security framework perspective, this vulnerability aligns with ATT&CK technique T1059.006 for Command and Scripting Interpreter: Python, and represents a clear example of how insecure deserialization can be exploited in configuration management systems. Organizations should also consider implementing automated vulnerability scanning and regular security assessments to identify similar issues in other components of their infrastructure that may be using unsafe YAML deserialization patterns.