CVE-2021-21694 is a critical-severity (CVSS 9.8) 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
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 agent-to-controller security subsystem limits which files on the Jenkins controller can be accessed by agent processes.
Multiple vulnerabilities in the file path filtering implementation of Jenkins 2.318 and earlier, LTS 2.303.2 and earlier allow agent processes to read and write arbitrary files on the Jenkins controller file system, and obtain some information about Jenkins controller file systems.
SECURITY-2541 / CVE-2021-21694: FilePath#toURI, FilePath#hasSymlink, FilePath#absolutize, FilePath#isDescendant, and FilePath#get*DiskSpace do not check any permissions.
We expect that most of these vulnerabilities have been present since SECURITY-144 was addressed in the 2014-10-30 security advisory.
Jenkins 2.319, LTS 2.303.3 addresses these security vulnerabilities.
SECURITY-2541 / CVE-2021-21694: FilePath#toURI, FilePath#hasSymlink, FilePath#absolutize, FilePath#isDescendant check stat permission. FilePath#get*DiskSpace methods are no longer allowed to be executed by an agent.
As some common operations are now newly subject to access control, it is expected that plugins sending commands from agents to the controller may start failing. Additionally, the newly introduced path canonicalization means that instances using a custom builds directory (Java system property jenkins.model.Jenkins.buildsDir) or partitioning JENKINS_HOME using symbolic links may fail access control checks. See the documentation for how to customize the configuration in case of problems.
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 |
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 2.303.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21694 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
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.
Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.Source: Red Hat security advisory for CVE-2021-21694 (CC BY 4.0)
| 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-2021-21694 in your dependencies?
Find it across Maven, including transitive dependencies.