CVE-2020-2166 in Pipeline: AWS Steps Plugin
Summary
by MITRE
Jenkins Pipeline: AWS Steps Plugin 1.40 and earlier does not configure its YAML parser to prevent the instantiation of arbitrary types, resulting in a remote code execution vulnerability.
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Analysis
by VulDB Data Team • 03/26/2020
The Jenkins Pipeline AWS Steps Plugin vulnerability CVE-2020-2166 represents a critical security flaw that enables remote code execution through improper YAML parsing configuration. This vulnerability affects versions 1.40 and earlier of the plugin, which is commonly used within Jenkins continuous integration and delivery environments to interact with Amazon Web Services. The flaw stems from the plugin's YAML parser implementation that fails to restrict the instantiation of arbitrary Java classes during deserialization processes. When Jenkins processes pipeline configurations containing malicious YAML content, the parser can inadvertently create and execute arbitrary objects, providing attackers with remote code execution capabilities. This issue particularly impacts organizations that utilize Jenkins pipelines for automated deployment workflows, where the plugin facilitates interactions with AWS services such as EC2, S3, and Lambda functions. The vulnerability is classified under CWE-502 as Deserialization of Untrusted Data, which is a well-known attack vector that has been exploited in numerous high-profile incidents. The security implications extend beyond simple code execution to include potential privilege escalation and lateral movement within compromised environments, as attackers can leverage the executed code to access additional system resources or escalate their privileges.
The technical exploitation of CVE-2020-2166 occurs when an attacker crafts malicious YAML content that includes serialized Java objects with specific class names. The plugin's YAML parser does not implement proper restrictions on the types of objects that can be instantiated during deserialization, allowing attackers to specify arbitrary class names that may include dangerous payloads such as command execution classes or malicious code containers. This vulnerability is particularly dangerous because it can be triggered through Jenkins pipeline configurations that are typically managed by authorized users, making it difficult to distinguish between legitimate and malicious pipeline scripts. The attack vector is consistent with techniques described in the ATT&CK framework under T1059.001 for Command and Scripting Interpreter, where adversaries execute code through legitimate system processes. The vulnerability can be exploited in various ways including through pipeline script uploads, configuration changes, or even through compromised Jenkins user accounts that have permission to modify pipeline definitions. The impact is amplified in environments where Jenkins is configured with elevated permissions or where the plugin is used to execute AWS commands that may have broad access to cloud resources.
Organizations affected by CVE-2020-2166 face significant operational risks including potential data breaches, system compromise, and unauthorized access to cloud resources. The vulnerability can enable attackers to execute arbitrary commands on the Jenkins server, potentially leading to complete system compromise and access to sensitive build artifacts, source code repositories, and deployment credentials. Attackers can leverage this vulnerability to establish persistent access, escalate privileges, or move laterally within the network infrastructure. The impact extends to cloud security posture as compromised Jenkins instances can be used to access AWS resources with potentially high-privilege credentials, leading to unauthorized resource consumption, data exfiltration, or service disruption. Organizations should immediately implement mitigations including upgrading to plugin versions 1.41 or later where the YAML parser has been properly configured to prevent arbitrary type instantiation. Additional defensive measures include implementing proper pipeline script validation, restricting Jenkins user permissions, and monitoring for unusual pipeline configuration changes. Security teams should also consider implementing network segmentation for Jenkins servers and regular vulnerability scanning to detect similar issues in other plugins or components. The remediation process should include thorough testing of updated plugin versions to ensure compatibility with existing pipeline configurations while maintaining operational continuity.