CVE-2021-21603: Jenkins core Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-98gq-6hxg-52r6
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CVSS 5.4
CWE-79
Published
Advisory Summary

CVE-2021-21603 is a MODERATE (CVSS 5.4) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Jenkins core libraries in the Maven ecosystem. The issue involves xss vulnerability in jenkins notification bar. Remediation is available by upgrading affected packages to version 2.275.

CVE-2021-21603 at a Glance

CVE Identifier CVE-2021-21603
GHSA Identifier GHSA-98gq-6hxg-52r6
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Jenkins core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.4

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:R/S:C/C:L/I:L/A:N).

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

How to Fix CVE-2021-21603

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: 2.275 
<dependency>
    <groupId>org.jenkins-ci.main</groupId>
    <artifactId>jenkins-core</artifactId>
    <version>2.275</version>
</dependency>
org.jenkins-ci.main:jenkins-core fixed: 2.275 
<dependency>
    <groupId>org.jenkins-ci.main</groupId>
    <artifactId>jenkins-core</artifactId>
    <version>2.275</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-2021-21603, 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 2.275), 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-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. 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 2.274 and earlier, LTS 2.263.1 and earlier does not escape notification bar response contents (typically shown after form submissions via Apply button). This results in a cross-site scripting (XSS) vulnerability exploitable by attackers able to influence notification bar contents. Jenkins 2.275, LTS 2.263.2 escapes the content shown in notification bars.

CVE-2021-21603 Affected Jenkins core Versions

2 component(s)
Fixed Versions:
2.275
Product / Package Ecosystem Affected Versions Fixed Version
org.jenkins-ci.main:jenkins-core
maven/org.jenkins-ci.main/jenkins-core
Maven
< 2.275
2.275
org.jenkins-ci.main:jenkins-core
maven/org.jenkins-ci.main/jenkins-core
Maven
≥ 2.263.2
< 2.275
2.275

References

NVD — CVE-2021-21603 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21603
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/jenkins/commit/f5d98421604e44f398e7de9d222b191a705608af
Jenkins core Source Repository REPOSITORY
https://github.com/jenkinsci/jenkins
Jenkins core Security Information SECURITY
https://www.jenkins.io/security/advisory/2021-01-13/#SECURITY-1889

Frequently Asked Questions

What is CVE-2021-21603?
CVE-2021-21603 is a security vulnerability in Jenkins core involving XSS vulnerability in Jenkins notification bar under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Jenkins core versions are affected?
Affected versions include releases prior to 2.275 across affected packages: org.jenkins-ci.main:jenkins-core.
What version fixes CVE-2021-21603?
Upgrading to 2.275 (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 2.275. Upgrade your dependency to 2.275 or later.
What is the CVSS score of CVE-2021-21603?
CVE-2021-21603 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2021-21603?
CVE-2021-21603 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Maven dependencies for CVE-2021-21603?
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-98gq-6hxg-52r6",
  "modified" : "2023-10-27T13:05:26Z",
  "published" : "2022-05-24T17:39:12Z",
  "aliases" : [ "CVE-2021-21603" ],
  "summary" : "XSS vulnerability in Jenkins notification bar",
  "details" : "Jenkins 2.274 and earlier, LTS 2.263.1 and earlier does not escape notification bar response contents (typically shown after form submissions via Apply button).\n\nThis results in a cross-site scripting (XSS) vulnerability exploitable by attackers able to influence notification bar contents.\n\nJenkins 2.275, LTS 2.263.2 escapes the content shown in notification bars.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.275"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "< 2.263.1"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.263.2"
      }, {
        "fixed" : "2.275"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.274"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-21603"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/jenkins/commit/f5d98421604e44f398e7de9d222b191a705608af"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jenkinsci/jenkins"
  }, {
    "type" : "WEB",
    "url" : "https://www.jenkins.io/security/advisory/2021-01-13/#SECURITY-1889"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-23T06:52:05Z",
    "nvd_published_at" : "2021-01-13T16:15:00Z"
  }
}