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             AUSCERT External Security Bulletin Redistribution

                   Jenkins Security Advisory 2021-10-06
                              7 October 2021


        AusCERT Security Bulletin Summary

Product:           Jenkins (core)
                   Git Plugin
Publisher:         Jenkins
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Cross-site Scripting           -- Remote with User Interaction
                   Provide Misleading Information -- Remote with User Interaction
                   Access Confidential Data       -- Remote with User Interaction
                   Reduced Security               -- Existing Account            
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-21684 CVE-2021-21683 CVE-2021-21682

Reference:         ASB-2018.0163

Original Bulletin: 

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Jenkins Security Advisory 2021-10-06  

This advisory announces vulnerabilities in the following Jenkins deliverables:

  o Jenkins (core)
  o Git Plugin


Improper handling of equivalent directory names on Windows  

SECURITY-2424 / CVE-2021-21682

Jenkins stores jobs and other entities on disk using their name shown on the UI
as file and folder names.

On Windows, when specifying a file or folder with a trailing dot character
(example.), the file or folder will be treated as if that character was not
present (example). As both are legal names for jobs and other entities in
Jenkins 2.314 and earlier, LTS 2.303.1 and earlier, this could allow users with
the appropriate permissions to change or replace configurations of jobs and
other entities.

Jenkins 2.315, LTS 2.303.2 does not allow names of jobs and other entities to
end with a dot character.

Jenkins core bundles vulnerable version of the commons-httpclient library  

SECURITY-2475 / CVE-2014-3577

Jenkins 2.314 and earlier, LTS 2.303.1 and earlier bundles a version of the
commons-httpclient library with the vulnerability CVE-2014-3577 that
incorrectly verified SSL/TLS certificates, making it susceptible to
man-in-the-middle attacks.

This library is widely used as a transitive dependency in Jenkins plugins.

The fix for CVE-2014-3577 was backported to the version of commons-httpclient
that is bundled in Jenkins 2.315, LTS 2.303.2 and made available to plugins.

Path traversal vulnerability on Windows  

SECURITY-2481 / CVE-2021-21683

The file browser for workspaces, archived artifacts, and userContent/ in
Jenkins 2.314 and earlier, LTS 2.303.1 and earlier may interpret some paths to
files as absolute on Windows.

This results in a path traversal vulnerability allowing attackers with Overall/
Read permission (Windows controller) or Job/Workspace permission (Windows
agents) to obtain the contents of arbitrary files.

The file browser in Jenkins 2.315, LTS 2.303.2 refuses to serve files that
would be considered absolute paths.

Stored XSS vulnerability in Git Plugin  

SECURITY-2499 / CVE-2021-21684

Git Plugin 4.8.2 and earlier does not escape the Git SHA-1 checksum parameters
provided to commit notifications when displaying them in a build cause.

This results in a stored cross-site scripting (XSS) vulnerability exploitable
by attackers able to submit crafted commit notifications to the /git/
notifyCommit endpoint.

Git Plugin 4.8.3 rejects Git SHA-1 checksum parameters that do not match the
expected format. Existing values are sanitized when displayed on the UI.

Note This vulnerability is only exploitable in Jenkins 2.314 and earlier, LTS
     2.303.1 and earlier. See the LTS upgrade guide.


  o SECURITY-2424: Medium
  o SECURITY-2475: Medium
  o SECURITY-2481: Medium
  o SECURITY-2499: High

Affected Versions  

  o Jenkins weekly up to and including 2.314
  o Jenkins LTS up to and including 2.303.1
  o Git Plugin up to and including 4.8.2


  o Jenkins weekly should be updated to version 2.315
  o Jenkins LTS should be updated to version 2.303.2
  o Git Plugin should be updated to version 4.8.3

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:

  o Daniel Beck, CloudBees, Inc. for SECURITY-2499
  o Mumin Koykiran for SECURITY-2481
  o Wadeck Follonier, CloudBees, Inc., Daniel Beck, CloudBees, Inc., and James
    Nord, CloudBees, Inc. for SECURITY-2424

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