Summary
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.
Impact
CVE-2021-21602 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. 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 (2.263.2, 2.275); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
org.jenkins-ci.main:jenkins-core to 2.263.2 or later; org.jenkins-ci.main:jenkins-core to 2.275 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2021-21602? CVE-2021-21602 is a medium-severity security vulnerability in org.jenkins-ci.main:jenkins-core (maven), affecting versions <= 2.263.1. It is fixed in 2.263.2, 2.275.
- How severe is CVE-2021-21602? CVE-2021-21602 has a CVSS score of 6.5 (Medium). 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.
- Which versions of org.jenkins-ci.main:jenkins-core are affected by CVE-2021-21602? org.jenkins-ci.main:jenkins-core (maven) versions <= 2.263.1 is affected.
- Is there a fix for CVE-2021-21602? Yes. CVE-2021-21602 is fixed in 2.263.2, 2.275. Upgrade to this version or later.
- Is CVE-2021-21602 exploitable, and should I be worried? Whether CVE-2021-21602 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
- What actually determines whether CVE-2021-21602 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.
- How do I fix CVE-2021-21602?
- Upgrade
org.jenkins-ci.main:jenkins-coreto 2.263.2 or later - Upgrade
org.jenkins-ci.main:jenkins-coreto 2.275 or later
- Upgrade