CVE-2017-1000088 in Jenkins
Summary
by MITRE
The Sidebar Link plugin allows users able to configure jobs, views, and agents to add entries to the sidebar of these objects. There was no input validation, which meant users were able to use javascript: schemes for these links.
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Analysis
by VulDB Data Team • 11/22/2019
The vulnerability identified as CVE-2017-1000088 resides within the Sidebar Link plugin functionality of Jenkins continuous integration and delivery platform. This issue represents a critical security flaw that enables authenticated users with job, view, and agent configuration privileges to inject malicious JavaScript code through sidebar link entries. The vulnerability stems from the complete absence of input validation mechanisms within the plugin's configuration interface, creating an avenue for arbitrary code execution through specially crafted hyperlink entries. The affected system operates under the assumption that legitimate users with appropriate permissions can be trusted, failing to implement proper sanitization of user-provided input before rendering it as part of the web interface.
The technical exploitation of this vulnerability occurs through the manipulation of hyperlink schemes within the sidebar configuration. Specifically, attackers can leverage the javascript: protocol to inject executable JavaScript code into sidebar entries, which then executes within the context of the victim's browser when the sidebar is rendered. This represents a classic cross-site scripting vulnerability that falls under CWE-79, which defines the weakness of cross-site scripting as the injection of malicious scripts into web applications. The vulnerability is particularly dangerous because it operates at the user interface level, bypassing traditional server-side security controls and directly targeting the client-side execution environment. The attack vector requires only that an attacker possess permissions to configure jobs, views, or agents within the Jenkins environment, making it accessible to users with relatively modest privileges.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to perform a wide range of malicious activities within the compromised Jenkins environment. Successful exploitation could enable attackers to steal session cookies, redirect users to malicious sites, modify sidebar content to mislead users, or even execute more sophisticated attacks such as credential harvesting or privilege escalation. The vulnerability affects the integrity and confidentiality of the Jenkins interface, potentially allowing attackers to gain unauthorized access to build artifacts, configuration data, and other sensitive information stored within the system. This weakness directly violates the principle of least privilege by allowing authenticated users to execute code that could compromise the entire Jenkins instance. The attack could also facilitate lateral movement within the organization's infrastructure if Jenkins is used as part of a larger CI/CD pipeline that interacts with other systems.
Mitigation strategies for CVE-2017-1000088 should focus on implementing proper input validation and sanitization mechanisms within the Sidebar Link plugin. Organizations should immediately upgrade to Jenkins versions that include patches addressing this vulnerability, as the official fix involves implementing strict validation of hyperlink schemes and preventing the use of javascript: protocols in sidebar entries. The recommended approach aligns with ATT&CK technique T1059.007, which addresses the mitigation of script injection attacks through proper input sanitization and validation. Security teams should also implement network-level controls to monitor for suspicious sidebar link configurations and establish strict access controls to prevent unauthorized users from gaining the necessary permissions to modify sidebar entries. Additionally, regular security auditing of Jenkins plugins and configurations should be conducted to identify similar vulnerabilities in other components of the CI/CD infrastructure. The implementation of Content Security Policy headers can provide an additional layer of defense by preventing the execution of inline scripts, though this should complement rather than replace proper input validation mechanisms.