Executive brief
Jenkins is an automation server widely used for continuous integration and deployment pipelines. The system log viewer in Jenkins does not properly escape log metadata (source, level, timestamp), allowing attackers who control agent processes to inject malicious scripts that execute in the browsers of administrators viewing logs. This could lead to session hijacking, credential theft, or further compromise of the Jenkins infrastructure.
Technical details
The vulnerability is a stored cross-site scripting (XSS) flaw in Jenkins' system log viewer component. The root cause is insufficient output encoding of log record metadata fields (source, level, timestamp) before rendering in HTML. Attackers with control over agent processes can inject JavaScript payloads into log records; when an administrator views the system logs, the malicious script executes in their browser context. No authentication is required beyond agent process control. The fix in Jenkins 2.580 and LTS 2.568.3 properly escapes these metadata fields. Content Security Policy (CSP) provides partial mitigation on Jenkins 2.539+ and LTS 2.541.1+.
Affected products
- Jenkins Jenkins 2.579 and earlier, LTS 2.568.2 and earlier
Timeline
- 2026-09-02: disclosed