Analysis Summary

A critical Cross-Site Scripting (XSS) vulnerability, tracked as CVE-2025-5806, has been identified in the Jenkins Gatling Plugin version 136.vb_9009b_3d33a_e, widely used for performance testing within Jenkins environments. The flaw arises from the plugin’s improper handling of Content-Security-Policy (CSP) headers when serving Gatling performance reports. Although CSP was introduced in Jenkins as a fundamental defense against XSS attacks (in versions 1.641 and 1.625.3), this plugin bypasses those protections entirely, allowing malicious scripts to execute within the Jenkins web interface. This bypass occurs due to the plugin processing and rendering user-controlled report content without enforcing proper CSP headers, enabling XSS vectors.

The vulnerability allows attackers to inject and execute arbitrary JavaScript within the Jenkins environment, provided they have the ability to modify Gatling report contents a privilege typically held by developers, QA engineers, or system administrators. If a targeted user views a crafted malicious report, the injected script could hijack sessions, steal credentials, or perform unauthorized administrative actions. The potential impact is severe, as Jenkins often sits at the core of CI/CD pipelines, meaning a compromise here could affect build configurations, deployment pipelines, and sensitive project data across an organization.

The CVSS v3.1 score of 8.1 (High) reflects the gravity of this issue, especially considering the lack of a patch at the time of disclosure. The Jenkins security team has confirmed that no fix is currently available for the vulnerable plugin version. Instead, they recommend downgrading to version 1.3.0 of the Gatling Plugin, which is not affected by this vulnerability. This mitigation is considered temporary but necessary until a permanent fix is released. The absence of a patch at disclosure time highlights the urgency for proactive measures by affected organizations.

In the meantime, organizations should audit their Jenkins instances to detect the presence of the vulnerable plugin version. If downgrading is not immediately feasible, security teams are advised to disable the Gatling Plugin temporarily. Enhanced monitoring for suspicious Jenkins activity, particularly around performance report viewing and editing, is also recommended. Additionally, reinforcing network segmentation, enforcing strict access controls, and limiting Jenkins' exposure to untrusted users are critical steps in reducing exploitation risk and mitigating the potential impact of this high-severity vulnerability.

Impact

• Sensitive Credential Theft
• Cross-Site Scripting
• Gain Access

Indicators of Compromise

CVE

• CVE-2025-5806

Affected Vendors

Remediation

• Upgrade to the latest version of the Jenkins Plugin, available from the Jenkins Security Advisory.
• Immediately downgrade the Jenkins Gatling Plugin to version 1.3.0, which is not affected by this vulnerability.
• If downgrading is not feasible, disable the Gatling Plugin until an official patch is released.
• Identify and assess all Jenkins environments using Gatling Plugin version 136.vb_9009b_3d33a_e to determine exposure.
• Implement enhanced monitoring for Gatling report generation and viewing activities to detect suspicious behavior.
• Review and restrict permissions so that only trusted users (e.g., developers, QA engineers) can modify report content.
• Use network segmentation and access controls to reduce the exposure of Jenkins instances to untrusted or public access.
• Monitor official Jenkins advisories for updates and patches related to the Gatling Plugin vulnerability.