CVE-2017-1000096 in Jenkins
Summary
by MITRE
Arbitrary code execution due to incomplete sandbox protection: Constructors, instance variable initializers, and instance initializers in Pipeline scripts were not subject to sandbox protection, and could therefore execute arbitrary code. This could be exploited e.g. by regular Jenkins users with the permission to configure Pipelines in Jenkins, or by trusted committers to repositories containing Jenkinsfiles.
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Analysis
by VulDB Data Team • 11/22/2019
This vulnerability exists within the Jenkins continuous integration and delivery platform where the sandbox protection mechanism fails to adequately secure pipeline script execution. The core flaw lies in the insufficient isolation of specific code elements within Jenkins pipeline configurations, particularly constructors, instance variable initializers, and instance initializers. These components operate outside the intended security boundaries that normally restrict script execution to prevent malicious activities. The vulnerability stems from a design oversight where these particular script elements were not properly sandboxed, allowing them to execute with elevated privileges despite the overall security model. This represents a critical bypass of Jenkins' security architecture that was intended to prevent unauthorized code execution within pipeline contexts.
The technical exploitation of this vulnerability occurs when a regular Jenkins user with pipeline configuration permissions or a trusted repository committer crafts a Jenkinsfile that leverages these unsandboxed elements. The constructors, instance variable initializers, and instance initializers can execute arbitrary code because they bypass the standard sandbox protections that normally restrict access to system resources, file operations, and network communications. Attackers can utilize this flaw to execute malicious commands, access restricted system functions, or perform unauthorized operations that would normally be blocked by Jenkins' security framework. The vulnerability specifically targets the pipeline script execution engine where these elements are processed, allowing them to operate outside the normal security constraints that protect the Jenkins environment from potentially harmful code execution.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to compromise the entire Jenkins infrastructure. Regular users who should normally be restricted from executing arbitrary code can leverage this flaw to gain unauthorized access to system resources, potentially leading to data breaches, system compromise, or further lateral movement within the network. The vulnerability affects organizations that rely heavily on Jenkins for automated builds and deployments, as it allows unauthorized code execution within pipeline contexts that are typically considered safe. This creates a significant risk for CI/CD environments where Jenkinsfiles are often managed by trusted parties who may not fully understand the security implications of their pipeline configurations. The flaw essentially allows attackers to execute code with the privileges of the Jenkins user, potentially leading to complete system compromise.
Mitigation strategies for this vulnerability require immediate attention through Jenkins version updates and patch deployment to address the sandboxing deficiencies in pipeline script execution. Organizations should implement strict access controls and audit pipeline configurations to prevent unauthorized modifications that could exploit this vulnerability. The recommended approach involves applying the official security patches released by Jenkins to correct the sandbox protection mechanisms. Additionally, administrators should consider implementing pipeline validation processes that review pipeline configurations for potentially malicious constructs before execution. The use of Jenkins security plugins and enhanced monitoring can help detect suspicious pipeline activities that may indicate exploitation attempts. Organizations should also review their Jenkins user permissions and implement the principle of least privilege to minimize the potential impact of compromised accounts. This vulnerability highlights the importance of comprehensive sandboxing mechanisms in CI/CD environments and aligns with CWE-254 security weaknesses related to inadequate sandbox protection. The flaw demonstrates how insufficient sandboxing can lead to arbitrary code execution, a pattern commonly addressed by ATT&CK techniques focusing on privilege escalation and code injection within build environments.