CVE-2020-2289 in Active Choices Plugin
Summary
by MITRE • 10/08/2020
Jenkins Active Choices Plugin 2.4 and earlier does not escape the name and description of build parameters, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with Job/Configure permission.
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Analysis
by VulDB Data Team • 11/17/2020
The vulnerability identified as CVE-2020-2289 affects the Jenkins Active Choices Plugin version 2.4 and earlier, representing a critical stored cross-site scripting weakness that undermines the security integrity of Jenkins continuous integration environments. This flaw resides within the plugin's handling of build parameter metadata, specifically failing to properly sanitize or escape the name and description fields of build parameters before storing and subsequently rendering them within the web interface. The vulnerability is particularly concerning because it allows attackers with minimal privileges - specifically the Job/Configure permission level - to execute malicious scripts against other users who view affected build parameter configurations.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding practices within the Active Choices Plugin's parameter handling mechanism. When administrators or users configure build parameters through the Jenkins interface, the plugin stores these parameter names and descriptions in its internal data structures without proper HTML escaping or sanitization. This stored data is then rendered back to users in various contexts including build parameter selection interfaces, job configuration pages, and parameterized build displays. The absence of proper output encoding creates an environment where maliciously crafted parameter names or descriptions containing script tags or other XSS payloads can be executed in the browser context of unsuspecting users who interact with these stored parameters.
From an operational impact perspective, this vulnerability exposes Jenkins environments to significant security risks as it enables attackers to perform various malicious activities through the execution of stored XSS payloads. An attacker with Job/Configure permissions can inject scripts that steal session cookies, redirect users to malicious websites, deface the Jenkins interface, or even execute additional attacks through the victim's privileged browser context. The stored nature of this vulnerability means that once an attacker successfully injects malicious content, the payload persists and affects all users who view the affected parameters, potentially compromising multiple users over extended periods. This makes the vulnerability particularly dangerous in environments where Jenkins is used for critical build processes and where multiple users regularly interact with job configurations.
The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software applications, and can be mapped to ATT&CK technique T1211, which covers the use of malicious scripts to gain unauthorized access to systems. Organizations using Jenkins with Active Choices Plugin versions prior to 2.5 are particularly at risk as this vulnerability has existed for extended periods without proper sanitization of user-supplied content. The exploitation requires only minimal privileges, making it accessible to users who typically have access to configure jobs but not necessarily administrative rights, which significantly expands the potential attack surface.
Mitigation strategies for this vulnerability include immediate upgrade to Active Choices Plugin version 2.5 or later, which implements proper input sanitization and output encoding mechanisms. Organizations should also implement additional security measures such as restricting Job/Configure permissions to only trusted users, implementing content security policies to limit script execution, and conducting regular security audits of Jenkins configurations. Administrators should consider implementing input validation at multiple layers including web application firewalls and Jenkins security configurations to provide defense-in-depth against similar vulnerabilities. Additionally, regular security training for Jenkins administrators and developers regarding secure coding practices and input validation can help prevent similar issues in other parts of the Jenkins ecosystem and prevent future occurrences of stored XSS vulnerabilities in related components.