CVE-2021-21623 is a medium-severity (CVSS 6.5) CWE-863 vulnerability in org.jenkins-ci.plugins:matrix-auth. A fix is available for org.jenkins-ci.plugins:matrix-auth — see the affected versions and patch details below.
Incorrect permission checks in Jenkins Matrix Authorization Strategy Plugin may allow accessing some items
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-2021-21623 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 379,145 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.plugins:matrix-authReal-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
Items (like jobs) can be organized hierarchically in Jenkins, using the Folders Plugin or something similar. An item is expected to be accessible only if all its ancestors are accessible as well.
Matrix Authorization Strategy Plugin 2.6.5 and earlier does not correctly perform permission checks to determine whether an item should be accessible.
This allows attackers with Item/Read permission on nested items to access them, even if they lack Item/Read permission for parent folders.\n\nMatrix Authorization Strategy Plugin 2.6.6 requires Item/Read permission on parent items to grant Item/Read permission on an individual item.
As a workaround in older releases, do not grant permissions on individual items to users who do not have access to parent items.
In case of problems, the Java system property hudson.security.AuthorizationMatrixProperty.checkParentPermissions can be set to false, completely disabling this fix.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.jenkins-ci.plugins:matrix-auth | all versions | 2.6.6org.jenkins-ci.plugins:matrix-auth:2.6.6 |
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.plugins:matrix-auth, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.jenkins-ci.plugins:matrix-auth to 2.6.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21623 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-2021-21623 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21623. 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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift Container Platform 4.8 | jenkins-0:2.289.1.1624020353-1.el8 | RHSA-2021:2437 |
Frequently Asked Questions
Is CVE-2021-21623 in your dependencies?
O3 Security finds CVE-2021-21623 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.