CVE-2026-84648 in Jenkins Plugin
Summary
by MITRE • 09/02/2026
In Jenkins 2.579 and earlier, LTS 2.568.2 and earlier, the system log viewer does not escape log record metadata (source, level, and timestamp) resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers in control of agent processes.
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Analysis
by VulDB Data Team • 09/02/2026
The identified vulnerability resides within the Jenkins continuous integration and deployment platform, specifically affecting versions 2.579 and earlier as well as Long Term Support releases up to version 2.568.2. This security flaw is classified as a stored cross-site scripting issue that stems from an improper neutralization of special elements used in web pages within the system log viewer component. The core technical deficiency lies in the failure to properly escape metadata associated with log records, specifically including fields such as source, level, and timestamp. When these data points are rendered for display in the user interface without adequate sanitization or encoding, they remain susceptible to injection attacks if malicious content is present within them.
The operational impact of this vulnerability is significant because it allows attackers who have gained control over agent processes to execute arbitrary scripts in the context of a victim's browser session. In Jenkins environments, agents are typically used to distribute build tasks across multiple machines. If an attacker compromises one of these agents and can manipulate the log output generated by that agent, they can inject malicious JavaScript payloads into the metadata fields mentioned above. Since this data is stored within the system logs and subsequently displayed in the web interface without proper escaping, any user who views the affected log entries will have their browser execute the injected code. This effectively turns a compromised build node into a vector for compromising the Jenkins master server or other users interacting with the platform through the web UI.
From an industry standards perspective, this vulnerability aligns closely with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific mechanism here involves stored XSS, where the malicious payload is saved on the target server and retrieved later when a user accesses the vulnerable page. In terms of attack tactics, this scenario maps to ATT&CK technique T1059, Command and Scripting Interpreter, specifically under sub-techniques involving JavaScript execution within a browser context. The exploitation chain relies heavily on the trust relationship between the Jenkins master and its agents, highlighting risks associated with lateral movement from compromised build infrastructure to administrative interfaces.
Mitigation strategies for this vulnerability primarily involve upgrading the Jenkins installation to version 2.580 or later for standard releases, or version 2.569.1 or later for Long Term Support branches. These updated versions include patches that ensure proper escaping of log record metadata before rendering it in the user interface. For organizations unable to immediately upgrade due to compatibility constraints with plugins or other system dependencies, temporary mitigations may involve restricting access to the Jenkins web UI through network-level controls such as firewalls or reverse proxies configured for authentication and IP whitelisting. Additionally, enforcing strict security policies on agent nodes is critical; this includes ensuring that only trusted users have permission to configure agents and monitoring agent processes for signs of compromise. Regular auditing of log sources and levels can also help in detecting anomalous entries that might indicate an attempted exploitation before it leads to successful code execution.