CVE-2020-2115 in NUnit Plugin
Summary
by MITRE
Jenkins NUnit Plugin 0.25 and earlier does not configure the XML parser to prevent XML external entity (XXE) attacks.
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Analysis
by VulDB Data Team • 02/13/2020
The Jenkins NUnit Plugin vulnerability identified as CVE-2020-2115 represents a critical security flaw in versions 0.25 and earlier that fails to properly configure XML parsers to mitigate XML external entity attacks. This vulnerability resides within the plugin's handling of XML data structures and demonstrates a classic XXE implementation where external entities are not properly restricted during XML processing. The issue stems from insufficient input validation and sanitization within the plugin's XML parser configuration, creating an attack surface that adversaries can exploit to manipulate XML processing behavior. The vulnerability allows attackers to craft malicious XML payloads that can trigger unintended XML parser behavior, potentially leading to sensitive data exposure, denial of service conditions, or server-side request forgery attacks. This flaw particularly impacts Jenkins environments where the NUnit plugin is installed and actively processing test result data, as the plugin's XML parsing functionality becomes a potential entry point for malicious actors seeking to compromise the build server infrastructure.
The technical implementation of this vulnerability aligns with CWE-611, which specifically addresses improper restriction of XML external entities, and demonstrates how inadequate XML parser configuration can create security risks in software applications. When the NUnit plugin processes XML test result files, it fails to disable external entity resolution and DTD processing, allowing attackers to inject malicious external entities that can reference local files, perform SSRF attacks against internal systems, or cause resource exhaustion through recursive entity references. The vulnerability operates at the parser level where XML documents are processed, making it particularly dangerous because it can be triggered through normal plugin operations when parsing test results from NUnit test executions. Attackers can leverage this weakness by crafting specially formatted XML test result files that contain malicious external entity declarations, which when processed by the vulnerable plugin can lead to unauthorized information disclosure or system compromise.
The operational impact of CVE-2020-2115 extends beyond simple data exposure, as it can enable attackers to perform reconnaissance on the underlying Jenkins server infrastructure, potentially leading to privilege escalation or lateral movement within the network. Organizations running vulnerable Jenkins instances with the NUnit plugin installed face significant risk of unauthorized access to build server resources, including potential exposure of source code repositories, build artifacts, and sensitive configuration data. The vulnerability can be exploited through various attack vectors including malicious test result uploads, compromised build jobs, or even through supply chain attacks if the plugin is used in automated build pipelines. Additionally, the impact is amplified in environments where Jenkins serves as a central automation hub for continuous integration and deployment processes, as successful exploitation could disrupt development workflows and potentially compromise the integrity of the entire software delivery pipeline.
Mitigation strategies for CVE-2020-2115 focus primarily on updating the Jenkins NUnit plugin to version 0.26 or later, which includes proper XML parser configuration that disables external entity resolution and DTD processing. Organizations should implement comprehensive patch management procedures to ensure all Jenkins plugins are kept current with security updates, particularly those handling XML data processing. Security hardening measures should include disabling unnecessary XML parser features, implementing proper input validation for all XML data, and monitoring plugin usage for suspicious activities. Network segmentation and access controls can help limit the potential impact of exploitation by restricting access to Jenkins servers and implementing principle of least privilege for plugin installations. Additionally, organizations should conduct regular security assessments of their Jenkins environments, including vulnerability scanning of installed plugins, and implement automated monitoring for unusual XML processing activities that could indicate exploitation attempts. The remediation process should also include reviewing and updating security policies to ensure proper plugin management and regular security assessments are part of the operational procedures, aligning with industry best practices and standards such as those recommended by NIST and OWASP for secure software development and deployment environments.