CVE-2021-21685 — jenkins-core
CRITICALCVE-2021-21685 is a critical-severity (CVSS 9.1) CWE-862 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.
Multiple vulnerabilities allow bypassing path filtering of agent-to-controller access control in Jenkins
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-2021-21685 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 377,333 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 2.318 and earlier, LTS 2.303.2 and earlier does not check agent-to-controller access to create parent directories in FilePath#mkdirs.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.jenkins-ci.main:jenkins-core | all versions | 2.303.3org.jenkins-ci.main:jenkins-core:2.303.3 |
| ☕Maven | org.jenkins-ci.main:jenkins-core | ≥ 2.304&&< 2.319 | 2.319org.jenkins-ci.main:jenkins-core:2.319 |
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 2.303.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21685 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-2021-21685 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21685. 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 3.11 | jenkins-0:2.303.3.1637698110-1.el7 | RHSA-2021:4827 |
| Red Hat OpenShift Container Platform 4.10 | jenkins-0:2.319.2.1643288987-1.el8 | RHSA-2022:0055 |
| Red Hat OpenShift Container Platform 4.6 | jenkins-0:2.303.3.1637597493-1.el8 | RHSA-2021:4799 |
| Red Hat OpenShift Container Platform 4.7 | jenkins-0:2.303.3.1637597018-1.el8 | RHSA-2021:4801 |
| Red Hat OpenShift Container Platform 4.8 | jenkins-0:2.303.3.1637596565-1.el8 | RHSA-2021:4829 |
| Red Hat OpenShift Container Platform 4.9 | jenkins-0:2.303.3.1637595827-1.el8 | RHSA-2021:4833 |
Frequently Asked Questions
Is CVE-2021-21685 in your dependencies?
O3 Security finds CVE-2021-21685 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.