CVE-2025-5806 is a high-severity cross-site scripting (XSS) vulnerability found in the Jenkins Gatling Plugin version 136.vb_9009b_3d33a_e. This plugin is used within Jenkins, a widely adopted open-source automation server for continuous integration and continuous delivery (CI/CD). The vulnerability arises because the plugin serves Gatling performance test reports in a way that bypasses the Content-Security-Policy (CSP) protections introduced in Jenkins versions 1.641 and 1.625. CSP is a security mechanism designed to prevent certain types of attacks, including XSS, by restricting the sources from which content can be loaded. By circumventing this protection, the plugin allows maliciously crafted report content to execute arbitrary JavaScript in the context of the Jenkins web interface. Exploitation requires that an attacker has privileges to modify or upload Gatling reports, which implies at least limited authenticated access (PR:L). The attack vector is network-based (AV:N), meaning it can be exploited remotely over the network. User interaction is required (UI:R), typically involving a user viewing the malicious report. The impact is severe, affecting confidentiality, integrity, and availability (C:H/I:H/A:H), as arbitrary script execution can lead to credential theft, session hijacking, unauthorized actions within Jenkins, or disruption of CI/CD pipelines. Although no known exploits are currently reported in the wild, the vulnerability's characteristics and high CVSS score (8.0) indicate a significant risk to Jenkins environments using the affected plugin version. The vulnerability is classified under CWE-79, which covers improper neutralization of input leading to XSS attacks.

For European organizations relying on Jenkins for their software development and deployment pipelines, this vulnerability poses a critical risk. Successful exploitation could allow attackers to execute arbitrary scripts within the Jenkins interface, potentially leading to unauthorized access to sensitive build configurations, credentials, and source code repositories. This could result in intellectual property theft, insertion of malicious code into software builds, or disruption of automated deployment processes. Given the central role of Jenkins in DevOps workflows, such an attack could cascade into broader operational impacts, including downtime and loss of trust in software integrity. Organizations in sectors with stringent regulatory requirements, such as finance, healthcare, and critical infrastructure, could face compliance violations and reputational damage if this vulnerability is exploited. The requirement for some level of authentication reduces the attack surface but does not eliminate risk, especially in environments with large user bases or insufficient access controls. The absence of known exploits in the wild provides a window for proactive mitigation, but the high severity demands urgent attention.

To mitigate CVE-2025-5806, European organizations should: 1) Immediately identify and inventory Jenkins instances using the Gatling Plugin version 136.vb_9009b_3d33a_e. 2) Apply any available patches or updates from the Jenkins project or plugin maintainers as soon as they are released. Since no patch links are currently available, monitor official Jenkins security advisories closely. 3) Restrict plugin usage and report upload permissions strictly to trusted users to minimize the risk of malicious report content being introduced. 4) Implement network segmentation and access controls to limit exposure of Jenkins servers to only necessary personnel and systems. 5) Enhance monitoring and logging around Jenkins activities, focusing on report uploads and user actions that could indicate exploitation attempts. 6) Educate Jenkins users about the risks of interacting with untrusted reports and encourage cautious behavior. 7) Consider temporary disabling or removing the vulnerable plugin if patching is not immediately feasible, balancing operational impact against security risk. 8) Review and strengthen Content-Security-Policy configurations at the Jenkins server level to mitigate potential bypasses. These steps go beyond generic advice by focusing on access control, monitoring, and operational adjustments tailored to the specific vulnerability context.