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CRITICAL severity

CVE-2021-21697 — jenkins-core

CRITICALFix: jenkinsci/jenkins@cf388d2

CVE-2021-21697 is a critical-severity (CVSS 9.1) vulnerability in org.jenkins-ci.main:jenkins-core. A fix is available for org.jenkins-ci.main:jenkins-core — see the affected versions and patch details below.

Agent-to-controller access control allows reading/writing most content of build directories in Jenkins

Also known asBIT-jenkins-2021-21697GHSA-cv2w-q8c3-xjv7
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs76th percentile — riskier than 76% of all scored CVEsHighest risk
0.96%1.34%1.72%2.10%1.5%1.6%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
☕org.jenkins-ci.main:jenkins-core☕org.jenkins-ci.main:jenkins-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Agents are allowed some limited access to files on the Jenkins controller file system. The directories agents are allowed to access in Jenkins 2.318 and earlier, LTS 2.303.2 and earlier include the directories storing build-related information, intended to allow agents to store build-related metadata during build execution. As a consequence, this allows any agent to read and write the contents of any build directory stored in Jenkins with very few restrictions (build.xml and some Pipeline-related metadata).

Jenkins 2.319, LTS 2.303.3 prevents agents from accessing contents of build directories unless it’s for builds currently running on the agent attempting to access the directory.

Update Pipeline: Nodes and Processes to version 2.40 or newer for Jenkins to associate Pipeline node blocks with the agent they’re running on for this fix.

If you are unable to immediately upgrade to Jenkins 2.319, LTS 2.303.3, you can install the Remoting Security Workaround Plugin. 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.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.jenkins-ci.main:jenkins-coreall versions2.303.3org.jenkins-ci.main:jenkins-core:2.303.3
☕Mavenorg.jenkins-ci.main:jenkins-core≥ 2.304&&< 2.3192.319org.jenkins-ci.main:jenkins-core:2.319

Affected Products

1 product · 2 configurations
Application
jenkinsjenkins
≤ 2.318
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.jenkins-ci.main:jenkins-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.jenkins-ci.main:jenkins-core to 2.303.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21697 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant
Workaround published by Red Hat
Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.
Source: Red Hat security advisory for CVE-2021-21697 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat OpenShift Container Platform 3.11jenkins-0:2.303.3.1637698110-1.el7RHSA-2021:4827
Red Hat OpenShift Container Platform 4.10jenkins-0:2.319.2.1643288987-1.el8RHSA-2022:0055
Red Hat OpenShift Container Platform 4.6jenkins-0:2.303.3.1637597493-1.el8RHSA-2021:4799
Red Hat OpenShift Container Platform 4.7jenkins-0:2.303.3.1637597018-1.el8RHSA-2021:4801
Red Hat OpenShift Container Platform 4.8jenkins-0:2.303.3.1637596565-1.el8RHSA-2021:4829
Red Hat OpenShift Container Platform 4.9jenkins-0:2.303.3.1637595827-1.el8RHSA-2021:4833

Frequently Asked Questions

Agents are allowed some limited access to files on the Jenkins controller file system. The directories agents are allowed to access in Jenkins 2.318 and earlier, LTS 2.303.2 and earlier include the directories storing build-related information, intended to allow agents to store build-related metadata during build execution. As a consequence, this allows any agent to read and write the contents of any build directory stored in Jenkins with very few restrictions (`build.xml` and some Pipeline-related metadata). Jenkins 2.319, LTS 2.303.3 prevents agents from accessing contents of build director
O3 Security · Impact-Aware SCA

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CVE-2021-21697: jenkins-core — Fixed in 2.303.3