CVE-2021-21697 is a critical-severity (CVSS 9.1) 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.
Agent-to-controller access control allows reading/writing most content of build directories 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-2021-21697 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 378,156 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
Agents are allowed some limited access to files on the Jenkins controller file system. The directories agents are allowed to access in Jenkins 2.318 and earlier, LTS 2.303.2 and earlier include the directories storing build-related information, intended to allow agents to store build-related metadata during build execution. As a consequence, this allows any agent to read and write the contents of any build directory stored in Jenkins with very few restrictions (build.xml and some Pipeline-related metadata).
Jenkins 2.319, LTS 2.303.3 prevents agents from accessing contents of build directories unless it’s for builds currently running on the agent attempting to access the directory.
Update Pipeline: Nodes and Processes to version 2.40 or newer for Jenkins to associate Pipeline node blocks with the agent they’re running on for this fix.
If you are unable to immediately upgrade to Jenkins 2.319, LTS 2.303.3, you can install the Remoting Security Workaround Plugin. It will prevent all agent-to-controller file access using FilePath APIs. Because it is more restrictive than Jenkins 2.319, LTS 2.303.3, more plugins are incompatible with it. Make sure to read the plugin documentation before installing it.
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-2021-21697 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-2021-21697 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21697. 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-2021-21697 in your dependencies?
O3 Security finds CVE-2021-21697 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.