CVE-2026-27099

Jenkins has a stored XSS vulnerability in node offline cause description

Jenkins 2.483 through 2.550 (both inclusive), LTS 2.492.1 through 2.541.1 (both inclusive) does not escape the user-provided description of the "Mark temporarily offline" offline cause, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with Agent/Configure or Agent/Disconnect permission.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2026-27099 has a CVSS score of 8.0 (High). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.551, 2.541.2); upgrading removes the vulnerable code path.

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1. What is CVE-2026-27099? CVE-2026-27099 is a high-severity cross-site scripting (XSS) vulnerability in org.jenkins-ci.main:jenkins-core (maven), affecting versions >= 2.542, < 2.551. It is fixed in 2.551, 2.541.2. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2026-27099? CVE-2026-27099 has a CVSS score of 8.0 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of org.jenkins-ci.main:jenkins-core are affected by CVE-2026-27099? org.jenkins-ci.main:jenkins-core (maven) versions >= 2.542, < 2.551 is affected.
4. Is there a fix for CVE-2026-27099? Yes. CVE-2026-27099 is fixed in 2.551, 2.541.2. Upgrade to this version or later.
5. Is CVE-2026-27099 exploitable, and should I be worried? Whether CVE-2026-27099 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-27099 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-27099?
   • Upgrade org.jenkins-ci.main:jenkins-core to 2.551 or later
   • Upgrade org.jenkins-ci.main:jenkins-core to 2.541.2 or later

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