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JenkinsApplication

CVE-2021-21696

CRITICAL · 9.8 CVSS v3.1 Published 2021-11-04
Fix available
A fix is available. Upgrade to after 2.318 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Jenkins 2.318 and earlier, LTS 2.303.2 and earlier does not limit agent read/write access to the libs/ directory inside build directories when using the FilePath APIs, allowing attackers in control of agent processes to replace the code of a trusted library with a modified variant. This results in unsandboxed code execution in the Jenkins controller process.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Jenkins before 2.318/LTS 2.303.2 does not restrict agent read/write access to the libs/ directory inside build directories via FilePath APIs. Attackers who compromise agent processes can replace trusted library code with malicious variants, achieving unsandboxed code execution on the Jenkins controller.

MitigationUpgrade Jenkins to version 2.318 or later, or LTS 2.303.3 or later, which includes proper access controls for agent FilePath access to build directories.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JenkinsApplication
Affected:<= 2.303.2<= 2.318

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Jenkins version
    Navigate to Manage Jenkins > About Jenkins in the web UI, or run 'java -jar jenkins.war --version' from the command line
    Affected if The displayed version is 2.318 or lower, or any LTS version 2.303.2 or lower
  2. Confirm agent connectivity is enabled
    Navigate to Manage Jenkins > Manage Nodes and verify that at least one agent (permanent or inbound) is configured and connected
    Affected if Agents are active and can communicate with the controller, as the vulnerability exploits agent-to-controller file access
  3. Check for custom library usage
    Navigate to Manage Jenkins > Configure System and look for the 'Additional Classpath' setting under the Global Pipeline Libraries section, or inspect pipeline scripts for @Library annotations
    Affected if Shared libraries are configured or used in pipelines, as the vulnerability targets the libs/ directory where these libraries are stored
  4. Verify build directory structure exists
    On the Jenkins controller file system, locate the $JENKINS_HOME/jobs/ directory and inspect for directories named 'libs' within build workspace folders
    Affected if Build directories contain libs/ subdirectories, which are the target of the unrestricted FilePath access

You are affected if your Jenkins version is 2.318 or lower (or LTS 2.303.2 or lower), agents are connected, and build workspaces with libs/ directories exist on the controller.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 2.318
Interim mitigation

Upgrade Jenkins to version 2.318 or later, or LTS 2.303.3 or later, which includes proper access controls for agent FilePath access to build directories.

Recommended fix High confidence

Jenkins 2.319 (weekly) or Jenkins LTS 2.303.3 (LTS)

  1. Upgrade Jenkins to version 2.319 or later if running a weekly release
  2. If running a Long Term Support (LTS) release, upgrade to Jenkins LTS 2.303.3 or later
  3. After upgrading, verify the controller is functioning correctly and review agent configurations

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Jenkins Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-21696 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data