CVE-2025-67635 is a vulnerability identified in Jenkins, a widely used open-source automation server for continuous integration and continuous delivery. The issue affects Jenkins versions 2.540 and earlier, including the Long-Term Support (LTS) release 2.528.2 and earlier. The root cause is improper handling of HTTP-based CLI connections when the connection stream becomes corrupted. Specifically, Jenkins fails to properly close these connections, which can be exploited by unauthenticated attackers to maintain open connections indefinitely. This behavior can lead to resource exhaustion on the Jenkins server, resulting in a denial of service (DoS) condition. The vulnerability does not require any authentication or user interaction, making it relatively easy to exploit remotely. Although there are no known exploits in the wild at the time of publication, the flaw poses a significant risk due to Jenkins' critical role in software development pipelines. The lack of a CVSS score indicates that the vulnerability is newly published and not yet fully assessed, but the technical details suggest a high impact on availability. The vulnerability primarily targets the Jenkins CLI over HTTP, which is often exposed internally or externally depending on organizational configurations. The flaw can disrupt continuous integration and deployment workflows, potentially delaying software releases and impacting business operations.

For European organizations, the impact of CVE-2025-67635 can be substantial, especially for those heavily reliant on Jenkins for their software development lifecycle. A successful denial of service attack could halt automated build, test, and deployment processes, leading to operational delays and increased downtime. This disruption could affect development teams, reduce productivity, and delay time-to-market for critical applications. In sectors such as finance, telecommunications, and manufacturing, where continuous integration pipelines are integral to rapid and secure software delivery, the impact could extend to compliance and service availability. Additionally, organizations with Jenkins instances exposed to the internet or insufficiently segmented networks are at higher risk. The vulnerability could also be leveraged as a diversion tactic in multi-stage attacks, distracting security teams while other threats are executed. Given the unauthenticated nature of the exploit, attackers do not need credentials, increasing the threat surface. The absence of known exploits currently provides a window for proactive mitigation before widespread exploitation occurs.

To mitigate CVE-2025-67635, European organizations should prioritize upgrading Jenkins to versions beyond 2.540 and LTS 2.528.2 once patches are released by the Jenkins Project. Until patches are available, organizations should restrict access to the Jenkins CLI interface by implementing network-level controls such as firewalls, VPNs, or IP whitelisting to limit exposure to trusted hosts only. Disabling the HTTP-based CLI if not required or switching to more secure communication methods (e.g., SSH-based CLI) can reduce risk. Monitoring and alerting on unusual connection patterns to the Jenkins server can help detect potential exploitation attempts. Organizations should also review and harden their Jenkins security configurations, including enabling authentication and authorization controls where possible. Regular backups and incident response plans should be updated to address potential service disruptions. Finally, educating development and operations teams about this vulnerability can ensure rapid response and remediation.