CVE-2020-2324 in CVS Plugin
Summary
by MITRE • 12/03/2020
Jenkins CVS Plugin 2.16 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.
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Analysis
by VulDB Data Team • 12/12/2020
The Jenkins CVS Plugin vulnerability identified as CVE-2020-2324 represents a critical security flaw that exposes systems to XML external entity attacks. This vulnerability affects versions 2.16 and earlier of the CVS plugin, which is commonly used within Jenkins continuous integration environments for version control operations. The issue stems from insufficient configuration of the XML parser component within the plugin, creating an attack surface that adversaries can exploit to manipulate XML processing behavior. When the plugin processes XML data from CVS repositories, it fails to properly restrict external entity resolution, allowing malicious actors to craft specially formatted XML content that can trigger unintended system behavior. The vulnerability specifically impacts the plugin's handling of XML documents during CVS operations, potentially enabling attackers to access local files, perform server-side request forgery attacks, or execute arbitrary code within the Jenkins environment.
The technical implementation of this vulnerability resides in the XML parser configuration within the CVS plugin's codebase, which does not disable external entity processing or restrict access to external resources during XML parsing operations. According to CWE-611, this vulnerability maps directly to improper restriction of XML external entities, a well-documented weakness that has been consistently exploited in various web applications and middleware systems. The flaw operates by allowing XML parsers to resolve external entities referenced in XML documents, which can include file system paths, network resources, or internal system information. Attackers can leverage this by submitting malicious XML content that references external entities pointing to sensitive files or services, effectively bypassing normal access controls and potentially extracting confidential information from the Jenkins server. The vulnerability's impact is amplified when the plugin processes untrusted XML data from CVS repositories, as the parsing occurs without proper security boundaries.
The operational impact of CVE-2020-2324 extends beyond simple data exposure, potentially enabling full system compromise within Jenkins environments. Attackers who successfully exploit this vulnerability can gain access to sensitive information stored within the Jenkins server, including build credentials, source code repositories, and configuration files that may contain authentication tokens or other security-sensitive data. The vulnerability can be exploited through various attack vectors, including manipulation of CVS repository data, injection of malicious XML payloads during build processes, or exploitation of the plugin's XML handling during repository synchronization operations. According to ATT&CK framework's T1190 technique, this vulnerability aligns with exploitation of remote services through XML parsing weaknesses, potentially allowing attackers to establish persistent access or escalate privileges within the CI/CD environment. The vulnerability is particularly concerning in enterprise environments where Jenkins serves as a central hub for automated builds and deployments, as compromise of the plugin could lead to unauthorized code deployment or complete access to the build infrastructure.
Organizations should implement immediate mitigations to address this vulnerability through patch management and configuration hardening. The primary remediation involves upgrading to Jenkins CVS Plugin version 2.17 or later, which includes proper XML parser configuration that disables external entity processing and prevents XXE attacks. Security administrators should also implement network segmentation and access controls to limit exposure of Jenkins servers to untrusted networks or users. Additional defensive measures include configuring Jenkins to use secure XML parsers with proper entity restrictions, implementing input validation for all XML data processed by the plugin, and monitoring for suspicious XML content in CVS repository operations. Organizations should conduct comprehensive vulnerability assessments to identify all instances of the affected plugin version and ensure proper patch deployment across all Jenkins environments. The mitigation strategy should also include regular security testing of XML processing components and implementation of security awareness training for developers who interact with Jenkins and CVS integration features.