CVE-2021-21677 in Code Coverage API Plugin
Summary
by MITRE • 08/31/2021
Jenkins Code Coverage API Plugin 1.4.0 and earlier does not apply Jenkins JEP-200 deserialization protection to Java objects it deserializes from disk, resulting in a remote code execution vulnerability.
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Analysis
by VulDB Data Team • 09/03/2021
The Jenkins Code Coverage API Plugin vulnerability identified as CVE-2021-21677 represents a critical security flaw that undermines the fundamental security architecture of the Jenkins continuous integration platform. This vulnerability specifically affects versions 1.4.0 and earlier of the Code Coverage API Plugin, which is widely used for tracking and reporting code coverage metrics in software development pipelines. The flaw resides in the plugin's improper handling of serialized Java objects, creating a pathway for remote code execution that could be exploited by malicious actors without authentication. The vulnerability directly contravenes established security best practices and represents a failure to implement proper deserialization safeguards that are essential for preventing unauthorized code execution in enterprise environments.
The technical root cause of this vulnerability stems from the plugin's failure to apply Jenkins JEP-200 deserialization protection mechanisms when processing serialized Java objects stored on disk. JEP-200, formally known as the "Prevent Deserialization Vulnerabilities" security enhancement, was implemented to address widespread deserialization attack vectors by enforcing strict validation and sanitization of serialized data. The Code Coverage API Plugin version 1.4.0 and earlier failed to incorporate these protections, allowing attackers to craft malicious serialized objects that could execute arbitrary code when the plugin deserializes data from disk. This deserialization flaw creates an attack surface where untrusted input can be transformed into executable commands, effectively bypassing the sandboxed execution environment that Jenkins typically provides. The vulnerability operates at the core of Java's serialization mechanism, where objects are converted into byte streams for storage or transmission, and back into objects at a later time, making it particularly dangerous when this process lacks proper validation.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with complete control over Jenkins servers and their underlying infrastructure. An attacker who successfully exploits this vulnerability can execute arbitrary commands with the privileges of the Jenkins service account, potentially leading to full system compromise and lateral movement within the network. This threat is particularly severe in enterprise environments where Jenkins servers often serve as central points for automated builds, deployments, and security scanning processes. The vulnerability affects the integrity and confidentiality of the entire CI/CD pipeline, as attackers could modify build processes, inject malicious code into production releases, or extract sensitive information from the Jenkins environment. The lack of authentication requirements for exploitation means that even unauthenticated attackers can leverage this vulnerability, significantly expanding the attack surface and making it particularly dangerous for publicly accessible Jenkins installations.
Organizations affected by this vulnerability should immediately implement multiple layers of mitigation strategies to protect their Jenkins environments from exploitation. The primary recommendation involves upgrading to Jenkins Code Coverage API Plugin version 1.4.1 or later, which includes the necessary JEP-200 deserialization protections. Additionally, administrators should implement network segmentation to limit access to Jenkins servers, disable unnecessary plugins, and enforce strict access controls through Jenkins' built-in security mechanisms. Security monitoring should be enhanced to detect anomalous deserialization activities and unusual command execution patterns. The vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1210 for Exploitation of Remote Services, demonstrating how this flaw can be leveraged for privilege escalation and persistent access. Organizations should also consider implementing automated patch management processes to ensure timely updates across their Jenkins infrastructure and establish incident response procedures specifically designed to handle deserialization-based attacks. Compliance with industry standards such as OWASP Top 10 and NIST SP 800-53 requires organizations to address such vulnerabilities through proper vulnerability management and security hardening practices, making this remediation essential for maintaining regulatory compliance and protecting enterprise assets.