CVE-2021-21639: Jenkins core Lack Of Type Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-pvwx-3jx5-24r2
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CVSS 4.3
CWE-20
Published
Advisory Summary

CVE-2021-21639 is a MODERATE (CVSS 4.3) lack of type validation vulnerability (CWE-20: Improper Input Validation) affecting Jenkins core libraries in the Maven ecosystem. The issue involves lack of type validation in agent related rest api in jenkins. Remediation is available by upgrading affected packages to version 2.277.2, 2.287.

CVE-2021-21639 at a Glance

CVE Identifier CVE-2021-21639
GHSA Identifier GHSA-pvwx-3jx5-24r2
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-20: Improper Input Validation
Affected Product Jenkins core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2021-21639

To remediate this vulnerability, upgrade all affected Jenkins core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.jenkins-ci.main:jenkins-core fixed: 2.277.2 
<dependency>
    <groupId>org.jenkins-ci.main</groupId>
    <artifactId>jenkins-core</artifactId>
    <version>2.277.2</version>
</dependency>
org.jenkins-ci.main:jenkins-core fixed: 2.287 
<dependency>
    <groupId>org.jenkins-ci.main</groupId>
    <artifactId>jenkins-core</artifactId>
    <version>2.287</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.jenkins-ci.main

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-21639, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.jenkins-ci.main

Analyze the terminal output to locate any version of Jenkins core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.277.2), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.jenkins-ci.main command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Jenkins core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Jenkins 2.286 and earlier, LTS 2.277.1 and earlier does not validate the type of object created after loading the data submitted to the `config.xml` REST API endpoint of a node. This allows attackers with Computer/Configure permission to replace a node with one of a different type. Jenkins 2.287, LTS 2.277.2 validates the type of object created and rejects objects of unexpected types.

CVE-2021-21639 Affected Jenkins core Versions

2 component(s)
Fixed Versions:
2.277.22.287
Product / Package Ecosystem Affected Versions Fixed Version
org.jenkins-ci.main:jenkins-core
maven/org.jenkins-ci.main/jenkins-core
Maven
< 2.277.2
2.277.2
org.jenkins-ci.main:jenkins-core
maven/org.jenkins-ci.main/jenkins-core
Maven
≥ 2.278
< 2.287
2.287

References

NVD — CVE-2021-21639 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21639
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/jenkins/commit/84210baed0c866bdee3e59271f98a767a14a5509
Jenkins core Source Repository REPOSITORY
https://github.com/jenkinsci/jenkins
Jenkins core Security Information SECURITY
https://www.jenkins.io/security/advisory/2021-04-07/#SECURITY-1721
Jenkins core Security Information SECURITY
http://www.openwall.com/lists/oss-security/2021/04/07/2

Frequently Asked Questions

What is CVE-2021-21639?
CVE-2021-21639 is a security vulnerability in Jenkins core involving Lack of type validation in agent related REST API in Jenkins under CWE-20: Improper Input Validation.
Which Jenkins core versions are affected?
Affected versions include releases prior to 2.277.2, 2.287 across affected packages: org.jenkins-ci.main:jenkins-core.
What version fixes CVE-2021-21639?
Upgrading to 2.277.2, 2.287 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jenkins-core affected?
Yes, org.jenkins-ci.main:jenkins-core is affected in releases prior to 2.277.2, 2.287. Upgrade your dependency to 2.277.2, 2.287 or later.
What is the CVSS score of CVE-2021-21639?
CVE-2021-21639 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2021-21639?
CVE-2021-21639 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check Maven dependencies for CVE-2021-21639?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.jenkins-ci.main'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pvwx-3jx5-24r2",
  "modified" : "2023-10-27T14:08:03Z",
  "published" : "2022-05-24T17:46:47Z",
  "aliases" : [ "CVE-2021-21639" ],
  "summary" : "Lack of type validation in agent related REST API in Jenkins",
  "details" : "Jenkins 2.286 and earlier, LTS 2.277.1 and earlier does not validate the type of object created after loading the data submitted to the `config.xml` REST API endpoint of a node.\n\nThis allows attackers with Computer/Configure permission to replace a node with one of a different type.\n\nJenkins 2.287, LTS 2.277.2 validates the type of object created and rejects objects of unexpected types.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.277.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.278"
      }, {
        "fixed" : "2.287"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.286"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-21639"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/jenkins/commit/84210baed0c866bdee3e59271f98a767a14a5509"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jenkinsci/jenkins"
  }, {
    "type" : "WEB",
    "url" : "https://www.jenkins.io/security/advisory/2021-04-07/#SECURITY-1721"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2021/04/07/2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-23T06:50:02Z",
    "nvd_published_at" : "2021-04-07T14:15:00Z"
  }
}