CVE-2016-0789 in Jenkins
Summary
by MITRE
CRLF injection vulnerability in the CLI command documentation in CloudBees Jenkins before 1.650 and LTS before 1.642.2 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via unspecified vectors.
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Analysis
by VulDB Data Team • 07/12/2022
The CVE-2016-0789 vulnerability represents a critical CRLF injection flaw within the command line interface documentation functionality of CloudBees Jenkins versions prior to 1.650 and LTS versions before 1.642.2. This vulnerability falls under the CWE-113 category, which specifically addresses improper neutralization of CRLF sequences in HTTP headers, making it a direct descendant of the well-known HTTP response splitting attack vector. The flaw exists in how Jenkins processes and displays command documentation, creating an opportunity for malicious actors to inject malicious HTTP headers into responses generated by the system.
The technical exploitation of this vulnerability occurs through the manipulation of command documentation parameters that are not properly sanitized before being included in HTTP responses. Attackers can craft malicious input that contains carriage return line feed sequences, which when processed by the vulnerable Jenkins instance, result in the injection of additional HTTP headers into the response. This injection capability enables attackers to perform HTTP response splitting attacks, where they can inject multiple HTTP responses within a single HTTP transaction, potentially leading to various downstream attacks including cache poisoning, cross-site scripting, and session hijacking.
The operational impact of this vulnerability extends beyond simple header injection, as it provides attackers with a foothold for more sophisticated attacks within the Jenkins environment. When combined with other vulnerabilities or used in conjunction with web cache poisoning techniques, this flaw can enable attackers to manipulate web caches, redirect users to malicious sites, or inject malicious content into responses that are subsequently cached by intermediate proxies or browsers. The vulnerability affects the core HTTP response handling mechanisms of Jenkins, making it particularly dangerous in environments where Jenkins serves as a central automation platform for continuous integration and deployment processes.
Mitigation strategies for CVE-2016-0789 primarily focus on immediate version upgrades to Jenkins 1.650 or LTS 1.642.2 and later releases, which contain the necessary patches to sanitize command documentation inputs and prevent CRLF sequence injection. Organizations should also implement network-level protections such as web application firewalls that can detect and block CRLF injection attempts, though these measures should be considered supplementary rather than primary defenses. The vulnerability demonstrates the importance of input validation in web applications, particularly in systems that process user-supplied data for display in HTTP responses, and aligns with ATT&CK technique T1190 which covers the exploitation of vulnerabilities in web applications through HTTP response manipulation. Additionally, implementing proper output encoding and sanitization practices for all user-facing content, combined with regular security audits of web application components, can help prevent similar vulnerabilities from emerging in other parts of the Jenkins ecosystem or related systems.