CVE-2015-7539 in Jenkins
Summary
by MITRE
The Plugins Manager in CloudBees Jenkins before 1.640 and LTS before 1.625.2 does not verify checksums for plugin files referenced in update site data, which makes it easier for man-in-the-middle attackers to execute arbitrary code via a crafted plugin.
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Analysis
by VulDB Data Team • 07/06/2022
The vulnerability identified as CVE-2015-7539 resides within the CloudBees Jenkins plugins manager component, specifically affecting versions prior to 1.640 for standard releases and 1.625.2 for Long Term Support editions. This security flaw represents a critical weakness in the software supply chain integrity mechanism that Jenkins employs to manage third-party plugins. The issue stems from the absence of cryptographic checksum verification during the plugin installation process, creating an exploitable condition that allows malicious actors to compromise the integrity of the plugin ecosystem. The vulnerability directly impacts the principle of secure software distribution by removing a fundamental security control that should validate the authenticity and integrity of downloaded components. This weakness enables attackers to manipulate plugin files during transit or at rest, potentially leading to arbitrary code execution within the Jenkins environment. The attack vector leverages man-in-the-middle techniques where adversaries can intercept and modify plugin distributions without detection, exploiting the trust relationship between the Jenkins instance and its update sites.
The technical implementation of this vulnerability occurs at the plugin verification layer within Jenkins's update mechanism. When Jenkins retrieves plugin metadata from update sites, it downloads the corresponding plugin files without performing cryptographic validation of the downloaded content. This process violates established security protocols that mandate checksum verification before executing any installation procedures. The flaw can be categorized under CWE-345: Insufficient Verification of Data Authenticity, which specifically addresses scenarios where systems fail to verify the integrity of data they receive from external sources. Additionally, the vulnerability aligns with CWE-327: Use of a Broken or Risky Cryptographic Algorithm, as the absence of proper checksum verification creates an environment where malicious modifications can occur undetected. The underlying architecture fails to implement proper cryptographic validation mechanisms that would normally be present in secure software distribution systems, leaving the Jenkins environment exposed to attacks that could compromise the entire build and deployment infrastructure.
The operational impact of CVE-2015-7539 extends far beyond simple code execution capabilities, as it fundamentally undermines the security posture of Jenkins instances that rely on third-party plugins for extended functionality. Attackers exploiting this vulnerability can install malicious plugins that provide backdoor access, data exfiltration capabilities, or complete system compromise of the Jenkins server. The implications are particularly severe in enterprise environments where Jenkins serves as a central automation hub for continuous integration and deployment processes. The vulnerability enables attackers to gain persistent access to critical build infrastructure, potentially compromising source code repositories, build artifacts, and deployment pipelines. From an attacker perspective, this vulnerability maps to several MITRE ATT&CK techniques including T1106: Execution through API, T1059: Command and Scripting Interpreter, and T1078: Valid Accounts, as compromised Jenkins instances often have elevated privileges and access to sensitive systems. The vulnerability affects not only individual plugin installations but can potentially compromise entire Jenkins clusters and their associated build environments, making it a particularly dangerous flaw in automated development workflows.
Mitigation strategies for CVE-2015-7539 require immediate version upgrades to Jenkins 1.640 or LTS 1.625.2, which implement proper checksum verification for plugin installations. Organizations should also implement additional network-level security controls including SSL certificate validation, network monitoring for suspicious plugin downloads, and regular security audits of installed plugins. The implementation of automated plugin integrity checking mechanisms and regular security scanning of the Jenkins environment should be prioritized. Security teams should establish baseline configurations that enforce plugin verification and maintain detailed inventory of all installed plugins with their corresponding checksums. Additionally, organizations should consider implementing network segmentation and access controls to limit exposure of Jenkins instances to untrusted networks. The vulnerability highlights the importance of maintaining up-to-date security practices and demonstrates the critical need for cryptographic integrity verification in all software distribution channels. Organizations should also implement security awareness training for developers who manage Jenkins configurations and plugin installations, as human factors often play a significant role in exploiting such vulnerabilities. The remediation process should include thorough testing of updated configurations to ensure that legitimate plugin installations continue to function properly while malicious modifications are properly detected and blocked.