CVE-2021-21693
First published: Thu Nov 04 2021(Updated: )
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-2539 / CVE-2021-21693: When creating temporary files, permission to create files is only checked after they’ve been created. We expect that most of these vulnerabilities have been present since [SECURITY-144 was addressed in the 2014-10-30 security advisory](https://www.jenkins.io/security/advisory/2014-10-30/). Jenkins 2.319, LTS 2.303.3 addresses these security vulnerabilities. SECURITY-2539 / CVE-2021-21693: When creating temporary files, permission to create files is checked before they are created based on an artificial path. 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](https://www.jenkins.io/doc/book/managing/system-properties/#jenkins-model-jenkins-buildsdir)) or partitioning `JENKINS_HOME` using symbolic links may fail access control checks. See [the documentation](https://www.jenkins.io/doc/book/security/controller-isolation/agent-to-controller/#file-access-rules) 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](https://www.jenkins.io/redirect/remoting-security-workaround/). 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.
Credit: jenkinsci-cert@googlegroups.com jenkinsci-cert@googlegroups.com jenkinsci-cert@googlegroups.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| maven/org.jenkins-ci.main:jenkins-core | <2.303.3 | 2.303.3 |
| maven/org.jenkins-ci.main:jenkins-core | >=2.304<=2.318 | 2.319 |
| Jenkins Jenkins | <2.303.3 | |
| Jenkins Jenkins | <2.319 | |
| redhat/jenkins | <2.319 | 2.319 |
| redhat/jenkins LTS | <2.303.3 | 2.303.3 |
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Reference Links
- https://nvd.nist.gov/vuln/detail/CVE-2021-21693
- https://www.jenkins.io/security/advisory/2021-11-04/#SECURITY-2455
- https://github.com/jenkinsci/jenkins/commit/104c751d907919dd53f5090f84d53c671a66457b
- https://github.com/jenkinsci/jenkins/commit/5a245e42979abe4a26d41727c839521e36cedd74
- https://github.com/jenkinsci/jenkins/commit/63cde2daadc705edf086f2213b48c8c547f98358
- https://github.com/advisories/GHSA-929w-q433-4h9x (Advisory)
- https://access.redhat.com/errata/RHSA-2021:4833
- https://access.redhat.com/errata/RHSA-2021:4829
- https://access.redhat.com/errata/RHSA-2021:4801
- https://access.redhat.com/errata/RHSA-2021:4799
- https://access.redhat.com/errata/RHSA-2021:4827
- https://access.redhat.com/security/cve/cve-2021-21693
- https://bugzilla.redhat.com/show_bug.cgi?id=2020341
Frequently Asked Questions
What is CVE-2021-21693?
CVE-2021-21693 is a vulnerability that allows agent-to-controller access to create temporary files in Jenkins 2.318 and earlier, LTS 2.303.2 and earlier.
How severe is CVE-2021-21693?
CVE-2021-21693 has a severity score of 9.8, which is considered critical.
How can I fix CVE-2021-21693?
To fix CVE-2021-21693, update Jenkins to version 2.319 or LTS to version 2.303.3.
Where can I find more information about CVE-2021-21693?
You can find more information about CVE-2021-21693 in the Jenkins security advisory and the Red Hat errata pages.
What is the CWE of CVE-2021-21693?
The CWE of CVE-2021-21693 is 863.
- collector/nvd-index
- collector/nvd-api
- collector/github-advisory-latest
- alias/GHSA-929w-q433-4h9x
- alias/CVE-2021-21693
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- agent/type
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- agent/softwarecombine
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- agent/software-canonical-lookup
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- collector/mitre-cve
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- package-manager/maven
- package-manager/redhat