CVE-2021-21695
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-2542 / CVE-2021-21695: `FilePath#listFiles` lists files outside directories with agent read access when following symbolic links. 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-2542 / CVE-2021-21695: `FilePath#listFiles` checks `stat` permission on files it returns, preventing listing files outside allowed directories. 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 |
|---|---|---|
| Jenkins Jenkins | <2.303.3 | |
| Jenkins Jenkins | <2.319 | |
| redhat/jenkins | <2.319 | 2.319 |
| redhat/jenkins LTS | <2.303.3 | 2.303.3 |
| 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 |
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Reference Links
- https://nvd.nist.gov/vuln/detail/CVE-2021-21695
- https://www.jenkins.io/security/advisory/2021-11-04/#SECURITY-2455
- http://www.openwall.com/lists/oss-security/2021/11/04/3
- https://github.com/jenkinsci/jenkins/commit/63cde2daadc705edf086f2213b48c8c547f98358
- https://github.com/advisories/GHSA-cvvm-4cr9-r436 (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-2021-21695
- https://bugzilla.redhat.com/show_bug.cgi?id=2020343
Frequently Asked Questions
What is CVE-2021-21695?
CVE-2021-21695 is a vulnerability in Jenkins that allows the listing of files outside allowed directories when following symbolic links.
How severe is CVE-2021-21695?
CVE-2021-21695 has a severity score of 8.8, indicating a high severity.
Which software versions are affected by CVE-2021-21695?
Jenkins 2.318 and earlier, LTS 2.303.2 and earlier are affected by CVE-2021-21695.
How can I fix CVE-2021-21695?
To fix CVE-2021-21695, upgrade Jenkins to version 2.319 or LTS 2.303.3.
Where can I find more information about CVE-2021-21695?
You can find more information about CVE-2021-21695 at the following references: [link1], [link2], [link3].
- agent/author
- agent/description
- agent/event
- agent/first-publish-date
- agent/last-modified-date
- agent/references
- agent/severity
- agent/softwarecombine
- agent/tags
- agent/type
- agent/weakness
- collector/github-advisory
- alias/GHSA-cvvm-4cr9-r436
- alias/CVE-2021-21695
- collector/github-advisory-latest
- collector/nvd-api
- collector/nvd-cve
- collector/nvd-index
- collector/redhat-bugzilla
- source/Red Hat
- agent/software-canonical-lookup
- package-manager/maven
- vendor/jenkins
- canonical/jenkins jenkins
- package-manager/redhat