Jenkins CLI Vulnerability: CVE-2025-67635 Uncovered

In the ever-evolving landscape of software development, staying ahead of security threats is paramount. Jenkins, a popular open-source automation server, is a critical tool for many development pipelines. Recently, a significant vulnerability, CVE-2025-67635, has been identified within the Jenkins Command Line Interface (CLI) component, specifically affecting the cli-2.107.2.jar library. This vulnerability carries a high severity rating with a CVSS score of 7.5, underscoring the urgency for developers to address it. Understanding the nature of this flaw, its potential impact, and the recommended remediation steps is crucial for maintaining the security and integrity of your Jenkins environment. This article delves into the details of CVE-2025-67635, offering insights into how it affects Jenkins and what actions you can take to protect your systems.

Understanding the Jenkins CLI Vulnerability: CVE-2025-67635

Let's dive deep into the vulnerability CVE-2025-67635 that impacts the Jenkins Command Line Interface (CLI), particularly within the cli-2.107.2.jar library. This vulnerability, identified in versions of Jenkins up to and including 2.540 and LTS versions up to 2.528.2, centers around how the CLI handles corrupted HTTP-based connections. The core issue is that the Jenkins CLI implementation fails to properly close these connections when the stream of data becomes corrupted. This oversight creates an opening for malicious actors. Specifically, unauthenticated attackers can exploit this weakness to trigger a denial of service (DoS) condition on the Jenkins server. Imagine a scenario where an attacker repeatedly sends malformed data, overwhelming the server's ability to manage these improperly closed connections. The result is that the server can become unresponsive, rendering it unusable for legitimate users and disrupting critical build and deployment processes. The fact that this attack can be launched by unauthenticated users significantly increases the risk, as it doesn't require any prior access or credentials to exploit. The CVSS score of 7.5 reflects the considerable impact this vulnerability can have on the availability of a Jenkins instance, which is often a central hub for an organization's software delivery lifecycle. The cli-2.107.2.jar is a component that facilitates remote interaction with Jenkins, making its security a direct concern for anyone managing Jenkins instances through its command-line interface. The dependency path identified, /pom.xml, indicates that this vulnerable library is likely declared as a dependency within the project's build configuration, a common practice in Java-based projects using Maven. The vulnerability was found in the HEAD commit of a specific repository (https://github.com/momo-tong/jenkins-2.107.2/commit/563109d6f2580e951e607392f61f164286254e11), highlighting a real-world instance where this vulnerable version was in use. The implications of a denial of service attack on a Jenkins server can be far-reaching, leading to significant downtime, delayed releases, and potential financial losses. Therefore, understanding the specifics of CVE-2025-67635 is the first step toward securing your Jenkins environment against such threats.

The Impact of CVE-2025-67635 on Your Jenkins Environment

The ramifications of CVE-2025-67635 extend beyond a simple technical flaw; they can have a tangible impact on your development operations and overall business continuity. A denial of service (DoS) attack, facilitated by this Jenkins CLI vulnerability, can bring your entire build and deployment pipeline to a grinding halt. Think about the critical role Jenkins plays in your organization – it’s the engine that drives automated testing, builds, and deployments. When Jenkins is unavailable, these essential processes stop. This means developers can't push code, testers can't run automated checks, and new releases can't be deployed to production. The immediate consequence is a significant disruption to development velocity. Projects can fall behind schedule, release windows might be missed, and customer satisfaction can suffer due to delays. For businesses reliant on frequent and rapid software releases, this downtime can translate directly into lost revenue and competitive disadvantage. Furthermore, the unauthenticated nature of this exploit is particularly concerning. It means that an attacker doesn't need to compromise any accounts or credentials within your Jenkins instance to initiate the attack. A vulnerability exposed to the network could be targeted by anyone with access to that network, even an external party if Jenkins is exposed to the internet without adequate security measures. This broadens the attack surface considerably and emphasizes the need for robust network security alongside application-level fixes. The CVSS score of 7.5, classified as 'High', is a clear indicator of the potential damage. It suggests that the vulnerability is both relatively easy to exploit (low attack complexity, no privileges required, no user interaction) and has a significant impact on the availability of the system. The cli-2.107.2.jar library, being part of the Jenkins CLI, means that any system interacting with Jenkins via its command-line interface is potentially at risk. This includes automated scripts, CI/CD tools, and even manual administrative actions performed through the CLI. The cascading effect of a compromised Jenkins server can be severe. It could lead to a loss of trust in your automated processes, forcing teams to revert to slower, manual methods, thereby negating the very benefits of using automation in the first place. In essence, addressing CVE-2025-67635 isn't just about fixing a bug; it's about safeguarding the operational efficiency, reliability, and security of your entire software development lifecycle.

Remediation Steps: Securing Your Jenkins Instance

Addressing CVE-2025-67635 requires a proactive approach to security, primarily focused on updating your Jenkins environment to a version that mitigates this vulnerability. The vulnerability lies within the Jenkins Command Line Interface (CLI), and the suggested fix involves upgrading specific Jenkins core components. The details provided indicate that remediation is possible by updating to newer versions of org.jenkins-ci.main:cli and org.jenkins-ci.main:jenkins-core. Specifically, the recommended versions are org.jenkins-ci.main:cli:2.541 and org.jenkins-ci.main:jenkins-core:2.541, or alternatively, org.jenkins-ci.main:cli:2.528.3 and org.jenkins-ci.main:jenkins-core:2.528.3. For projects using Maven, this typically means updating the pom.xml file to reflect these new dependency versions. You would locate the relevant entries for jenkins-core and cli and change their versions to one of the suggested secure versions. It's important to note that while the fix is available, the report indicates that a remediation pull request could not be automatically created for this specific vulnerability. This means manual intervention is required. Before implementing any updates, it's always a best practice to test the new versions in a staging or development environment to ensure compatibility with your existing build jobs and plugins. Unexpected issues can arise during upgrades, and thorough testing can prevent disruptions to your production pipeline. Additionally, review your Jenkins security configuration. While updating is the primary remediation, ensure that network access to your Jenkins instance is appropriately restricted. Limiting access to trusted IP addresses or internal networks can provide an additional layer of defense against potential attacks, even before a patch is applied. Regularly scanning your dependencies for known vulnerabilities using tools like the one that identified this issue is also a crucial part of a robust security strategy. Staying informed about new threats and promptly applying fixes will help maintain the security posture of your Jenkins environment and protect your development workflows from disruption. The information about the vulnerability was published on 2025-12-10, and the fix resolution details provide clear version numbers, making the upgrade process straightforward for those who follow the recommended steps.

Conclusion: Proactive Security for Jenkins

The discovery of CVE-2025-67635 in the Jenkins CLI, specifically affecting cli-2.107.2.jar, serves as a vital reminder of the ongoing need for vigilance in software security. This high-severity vulnerability, with its potential for unauthenticated denial of service attacks, underscores the importance of keeping your Jenkins environment up-to-date and secure. By understanding the details of this exploit and promptly applying the recommended fixes – upgrading to versions like 2.541 or 2.528.3 of jenkins-core and cli – you can significantly reduce your risk exposure. Proactive security is not a one-time task but an ongoing process. Regularly reviewing your dependencies, implementing robust security configurations, and staying informed about newly disclosed vulnerabilities are essential practices for maintaining a secure and reliable CI/CD pipeline. Protecting your Jenkins instance means protecting your development velocity, your release schedule, and ultimately, your business operations.

For further information on Jenkins security and best practices, you can refer to the official Jenkins Security Advisories. Staying informed with resources like these is key to maintaining a strong security posture in the face of evolving threats.