This advisory announces vulnerabilities in the following Jenkins deliverables:
Jenkins 2.270 through 2.393 (both inclusive), LTS 2.277.1 through 2.375.3 (both inclusive) does not escape the Jenkins version a plugin depends on when rendering the error message stating its incompatibility with the current version of Jenkins in the plugin manager.
This results in a stored cross-site scripting (XSS) vulnerability exploitable by attackers able to provide plugins to the configured update sites and have this message shown by Jenkins instances.
| Exploitation does not require the manipulated plugin to be installed. |
Jenkins 2.394, LTS 2.375.4, and LTS 2.387.1 escapes the Jenkins version a plugin depends on when rendering the error message stating its incompatibility with the current version of Jenkins.
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Due to how Jenkins community update sites serve plugin metadata based on the reported Jenkins core version, it is unlikely that a reasonably up to date Jenkins instance shows the vulnerable error message in the plugin manager at all. At least one of the following conditions needs to be met:
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| Jenkins community update sites no longer publish plugin releases with invalid Jenkins core dependencies since 2023-02-15. This prevents exploitation through those update sites even on versions of Jenkins older than 13 months. Additionally, the Jenkins security team has confirmed that no plugin release with a core dependency manipulated to exploit this vulnerability has ever been published by the Jenkins project. |
Jenkins creates a temporary file when a plugin is uploaded from an administrator’s computer.
Jenkins 2.393 and earlier, LTS 2.375.3 and earlier creates this temporary file in the system temporary directory with the default permissions for newly created files.
If these permissions are overly permissive, they may allow attackers with access to the Jenkins controller file system to read and write the file before it is installed in Jenkins, potentially resulting in arbitrary code execution.
| This vulnerability only affects operating systems using a shared temporary directory for all users (typically Linux). Additionally, the default permissions for newly created files generally only allows attackers to read the temporary file. |
Jenkins 2.394, LTS 2.375.4, and LTS 2.387.1 creates the temporary file with more restrictive permissions.
As a workaround, you can set a different path as your default temporary directory using the Java system property java.io.tmpdir, if you’re concerned about this issue but unable to immediately update Jenkins.
Jenkins 2.393 and earlier, LTS 2.375.3 and earlier is affected by the Apache Commons FileUpload library’s vulnerability CVE-2023-24998.
This library is used to process uploaded files via the Stapler web framework (usually through StaplerRequest#getFile) and MultipartFormDataParser in Jenkins.
This allows attackers to cause a denial of service (DoS) by sending crafted requests to HTTP endpoints processing file uploads.
Jenkins 2.394, LTS 2.375.4, and LTS 2.387.1 limits the number of request parts to be processed to 1000. Specific endpoints receiving only simple form submissions have a lower limit.
| While the Apache Commons FileUpload dependency has been updated previously in the 2.392 weekly release, the Jenkins-specific changes in 2.394 are necessary for Jenkins to be protected. |
Some Jenkins forms can be very complex, and these limits apply to all fields and not just fields representing uploaded files.
As a result, legitimate submissions of complex forms that include (possible) file uploads may be affected by these limits.
If that happens, these limits can be changed by setting the Java system properties hudson.util.MultipartFormDataParser.FILEUPLOAD_MAX_FILES and org.kohsuke.stapler.RequestImpl.FILEUPLOAD_MAX_FILES to a bigger value, or to -1 to completely disable them.
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These releases of Jenkins also introduce additional Java system properties that can be set to restrict request sizes:
By default, Jenkins does not set these size limits. Setting these system properties can offer additional protection, but comes at a greater risk of impacting legitimate use (e.g., when uploading huge file parameters). |
Jenkins uses temporary directories adjacent to workspace directories, usually with the @tmp name suffix, to store temporary files related to the build.
In pipelines, these temporary directories are adjacent to the current working directory when operating in a subdirectory of the automatically allocated workspace.
Jenkins-controlled processes, like SCMs, may store credentials in these directories.
Jenkins 2.393 and earlier, LTS 2.375.3 and earlier shows these temporary directories when viewing job workspaces, which allows attackers with Item/Workspace permission to access their contents.
Jenkins 2.394, LTS 2.375.4, and LTS 2.387.1 does not list these temporary directories in job workspaces.
As a workaround, do not grant Item/Workspace permission to users who lack Item/Configure permission, if you’re concerned about this issue but unable to immediately update Jenkins.
The Java system property hudson.model.DirectoryBrowserSupport.allowTmpEscape can be set to true to restore the previous behavior.
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When triggering a build from the Jenkins CLI, Jenkins creates a temporary file on the controller if a file parameter is provided through the CLI’s standard input.
Jenkins 2.393 and earlier, LTS 2.375.3 and earlier creates this temporary file in the default temporary directory with the default permissions for newly created files.
If these permissions are overly permissive, they may allow attackers with access to the Jenkins controller file system to read and write the file before it is used in the build.
| This vulnerability only affects operating systems using a shared temporary directory for all users (typically Linux). Additionally, the default permissions for newly created files generally only allows attackers to read the temporary file. |
Jenkins 2.394, LTS 2.375.4, and LTS 2.387.1 creates the temporary file with more restrictive permissions.
As a workaround, you can set a different path as your default temporary directory using the Java system property java.io.tmpdir, if you’re concerned about this issue but unable to immediately update Jenkins.
Jenkins 2.393 and earlier, LTS 2.375.3 and earlier prints an error stack trace on agent-related pages when agent connections are broken. This stack trace may contain information about Jenkins configuration that is otherwise inaccessible to attackers.
Jenkins 2.394, LTS 2.375.4, and LTS 2.387.1 does not display error stack traces when agent connections are broken.
update-center2 is the tool used to generate the Jenkins update sites hosted on updates.jenkins.io.
| While it is designed for use by the Jenkins project for this purpose, others may be using it to operate their own self-hosted update sites. |
update-center2 3.13 and 3.14 renders the required Jenkins core version on plugin download index pages (pages like this). This version is taken from plugin metadata without being sanitized.
This results in a stored cross-site scripting (XSS) vulnerability exploitable by attackers able to provide a plugin for hosting.
The following preconditions must both be satisfied for this to be exploitable in a self-hosted update-center2:
The generation of download pages needs to be enabled (i.e., the --download-links-directory argument needs to be set).
A custom download page template must be used (--index-template-url argument), and the template used must not prevent JavaScript execution through Content-Security-Policy.
The default template prevents exploitation by declaring a restrictive Content-Security-Policy.
update-center2 3.15 filters out plugin releases with invalid Jenkins core dependencies.
Administrators hosting their own update sites using update-center2 or a fork thereof are advised to update it, or integrate the commit 091ef999.
| This change has been deployed to Jenkins community update sites on 2023-02-15. The Jenkins project has distributed a single plugin release, that exploited this vulnerability in a harmless way to demonstrate the issue, for two hours on 2023-01-16. No other plugin releases that exploit this vulnerability have been published. |
These versions include fixes to the vulnerabilities described above. All prior versions are considered to be affected by these vulnerabilities unless otherwise indicated.
The Jenkins project would like to thank the reporters for discovering and reporting these vulnerabilities: