CVE-2021-21602 is a medium-severity (CVSS 6.5) CWE-59 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.
Arbitrary file read vulnerability in workspace browsers in Jenkins
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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
The file browser for workspaces, archived artifacts, and $JENKINS_HOME/userContent/ follows symbolic links to locations outside the directory being browsed in Jenkins 2.274 and earlier, LTS 2.263.1 and earlier.
This allows attackers with Job/Workspace permission and the ability to control workspace contents (e.g., with Job/Configure permission or the ability to change SCM contents) to create symbolic links that allow them to access files outside workspaces using the workspace browser.
This issue is caused by an incomplete fix for SECURITY-904 / CVE-2018-1000862 in the 2018-12-08 security advisory.
Jenkins 2.275, LTS 2.263.2 no longer supports symlinks in workspace browsers. While they may still exist on the file system, they are no longer shown on the UI, accessible via URLs, or included in directory content downloads.
This fix only changes the behavior of the Jenkins UI. Archiving artifacts still behaves as before.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.jenkins-ci.main:jenkins-core | all versions | 2.263.2org.jenkins-ci.main:jenkins-core:2.263.2 |
| ☕Maven | org.jenkins-ci.main:jenkins-core | ≥ 2.264&&< 2.275 | 2.275org.jenkins-ci.main:jenkins-core:2.275 |
Affected Products
jenkinsjenkinsDetection & 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 2.263.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21602 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.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift Container Platform 3.11 | jenkins-0:2.263.3.1612433584-1.el7 | RHSA-2021:0637 |
| Red Hat OpenShift Container Platform 4.5 | conmon-2:2.0.21-1.rhaos4.5.el7 | RHSA-2021:0429 |
| Red Hat OpenShift Container Platform 4.6 | jenkins-0:2.263.3.1612434510-1.el8 | RHSA-2021:0423 |
| Red Hat OpenShift Container Platform 4.8 | atomic-openshift-service-idler-0:4.8.0-202106281541.p0.git.39cfc66.assembly.stream.el8 | RHSA-2021:2437 |
Frequently Asked Questions
Is CVE-2021-21602 in your dependencies?
Find it across Maven, including transitive dependencies.