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-2485 / CVE-2021-21689: `FilePath#unzip` and `FilePath#untar` were not subject to any access control. 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-2485 / CVE-2021-21689: `FilePath#unzip` and `FilePath#untar` are now subject to access control. 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 |
Sign up to SecAlerts for real-time vulnerability data matched to your software, aggregated from hundreds of sources.
CVE-2021-21689 is a vulnerability in Jenkins that allows unauthenticated remote attackers to access Jenkins agents.
CVE-2021-21689 has a severity level of critical (9.1).
Jenkins versions up to and including 2.318 and LTS versions up to and including 2.303.2 are affected by CVE-2021-21689.
To fix CVE-2021-21689, you need to upgrade to Jenkins version 2.319 or LTS version 2.303.3 or higher.
You can find more information about CVE-2021-21689 in the Jenkins security advisory and the Red Hat security advisories.