CVE-2026-27099 is a high-severity (CVSS 8) Cross-site Scripting (XSS) vulnerability in org.jenkins-ci.main:jenkins-core. A fix is available for org.jenkins-ci.main:jenkins-core — see the affected versions and patch details below.
Jenkins has a stored XSS vulnerability in node offline cause description
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27099.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-27099 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.jenkins-ci.main:jenkins-core☕org.jenkins-ci.main:jenkins-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.jenkins-ci.main:jenkins-core | ≥ 2.542&&< 2.551 | 2.551org.jenkins-ci.main:jenkins-core:2.551 |
| ☕Maven | org.jenkins-ci.main:jenkins-core | ≥ 2.483&&< 2.541.2 | 2.541.2org.jenkins-ci.main:jenkins-core:2.541.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.jenkins-ci.main:jenkins-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.jenkins-ci.main:jenkins-core to 2.551 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27099 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-27099 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-27099. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability in Jenkins allows authenticated attackers with Agent/Configure or Agent/Disconnect permissions to inject malicious scripts into the "Mark temporarily offline" cause description. This stored cross-site scripting (XSS) flaw can lead to information disclosure or unauthorized actions within a user's…
| Product | Fixed in | Advisory |
|---|---|---|
| OpenShift Developer Tools and Services 4.12 | ocp-tools-4/jenkins-rhel8:1776764096 | RHSA-2026:10209 |
| OpenShift Developer Tools and Services 4.13 | ocp-tools-4/jenkins-rhel8:1776764096 | RHSA-2026:10201 |
| OpenShift Developer Tools and Services 4.14 | ocp-tools-4/jenkins-rhel8:1776762347 | RHSA-2026:10211 |
| OpenShift Developer Tools and Services 4.15 | ocp-tools-4/jenkins-rhel8:1776762347 | RHSA-2026:10204 |
| OpenShift Developer Tools and Services 4.16 | ocp-tools-4/jenkins-rhel9:1776944215 | RHSA-2026:10214 |
| OpenShift Developer Tools and Services 4.17 | ocp-tools-4/jenkins-rhel9:1776944215 | RHSA-2026:10213 |
| OpenShift Developer Tools and Services 4.18 | ocp-tools-4/jenkins-rhel9:1776944215 | RHSA-2026:10215 |
| OpenShift Developer Tools and Services 4.19 | ocp-tools-4/jenkins-rhel9:1776944215 | RHSA-2026:10206 |
Frequently Asked Questions
Is CVE-2026-27099 in your dependencies?
O3 Security finds CVE-2026-27099 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.