CVE-2020-2100: Jenkins core Jenkins Vulnerable To UDP Amplification Vulnerability

MODERATE
Advisory Identifier: GHSA-gpxv-776p-7gc7
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CVSS 5.8
CWE-406
Published
Advisory Summary

CVE-2020-2100 is a MODERATE (CVSS 5.8) jenkins vulnerable to udp amplification vulnerability (CWE-406: Insufficient Control of Network Message Volume (Network Amplification)) affecting Jenkins core libraries in the Maven ecosystem. The issue involves jenkins vulnerable to udp amplification reflection attack. Remediation is available by upgrading affected packages to version 2.204.2, 2.219.

CVE-2020-2100 at a Glance

CVE Identifier CVE-2020-2100
GHSA Identifier GHSA-gpxv-776p-7gc7
Severity MODERATE
CVSS v3.1 Base Score 5.8
CWE Classification CWE-406: Insufficient Control of Network Message Volume (Network Amplification)
Affected Product Jenkins core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L).

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

How to Fix CVE-2020-2100

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: 2.204.2 
<dependency>
    <groupId>org.jenkins-ci.main</groupId>
    <artifactId>jenkins-core</artifactId>
    <version>2.204.2</version>
</dependency>
org.jenkins-ci.main:jenkins-core fixed: 2.219 
<dependency>
    <groupId>org.jenkins-ci.main</groupId>
    <artifactId>jenkins-core</artifactId>
    <version>2.219</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-2020-2100, 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 2.204.2), 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-406: Insufficient Control of Network Message Volume (Network Amplification), where the product does not sufficiently monitor or control transmitted network traffic volume, so that an actor can cause the product to transmit more traffic than should be allowed for that actor. 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 2.218 and earlier, LTS 2.204.1 and earlier supports two network discovery services (UDP multicast/broadcast and DNS multicast) by default. The UDP multicast/broadcast service can be used in an amplification reflection attack, as very few bytes sent to the respective endpoint result in much larger responses: A single byte request to this service would respond with more than 100 bytes of Jenkins metadata which could be used in a DDoS attack on a Jenkins controller. Within the same network, spoofed UDP packets could also be sent to make two Jenkins controllers go into an infinite loop of replies to one another, thus causing a denial of service. Jenkins 2.219, LTS 2.204.2 now disables both UDP multicast/broadcast and DNS multicast by default. Administrators that need these features can re-enable them again by setting the system property `hudson.DNSMultiCast.disabled` to `false` (for DNS multicast) or the system property `hudson.udp` to `33848`, or another port (for UDP broadcast/multicast). These are the same system properties that controlled whether these features were enabled in the past, so any instances explicitly enabling these features by setting these system properties will continue to have them enabled.

CVE-2020-2100 Affected Jenkins core Versions

2 component(s)
Fixed Versions:
2.204.22.219
Product / Package Ecosystem Affected Versions Fixed Version
org.jenkins-ci.main:jenkins-core
maven/org.jenkins-ci.main/jenkins-core
Maven
< 2.204.2
2.204.2
org.jenkins-ci.main:jenkins-core
maven/org.jenkins-ci.main/jenkins-core
Maven
≥ 2.205
< 2.219
2.219

References

NVD — CVE-2020-2100 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-2100
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/jenkins/commit/cd28a6d9347228b03da0e45653e23032342c2a36
access.redhat.com/errata/rhba-2020:04... WEB
https://access.redhat.com/errata/RHBA-2020:0402
access.redhat.com/errata/rhba-2020:06... WEB
https://access.redhat.com/errata/RHBA-2020:0675
access.redhat.com/errata/rhsa-2020:06... WEB
https://access.redhat.com/errata/RHSA-2020:0681
access.redhat.com/errata/rhsa-2020:06... WEB
https://access.redhat.com/errata/RHSA-2020:0683
Jenkins core Source Repository REPOSITORY
https://github.com/jenkinsci/jenkins
Jenkins core Security Information SECURITY
https://jenkins.io/security/advisory/2020-01-29/#SECURITY-1641
Jenkins core Security Information SECURITY
http://www.openwall.com/lists/oss-security/2020/01/29/1

Frequently Asked Questions

What is CVE-2020-2100?
CVE-2020-2100 is a security vulnerability in Jenkins core involving Jenkins vulnerable to UDP amplification reflection attack under CWE-406: Insufficient Control of Network Message Volume (Network Amplification).
Which Jenkins core versions are affected?
Affected versions include releases prior to 2.204.2, 2.219 across affected packages: org.jenkins-ci.main:jenkins-core.
What version fixes CVE-2020-2100?
Upgrading to 2.204.2, 2.219 (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 2.204.2, 2.219. Upgrade your dependency to 2.204.2, 2.219 or later.
What is the CVSS score of CVE-2020-2100?
CVE-2020-2100 has a CVSS v3.1 base score of 5.8 (MODERATE) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L.
What CWE is associated with CVE-2020-2100?
CVE-2020-2100 is classified under CWE-406: Insufficient Control of Network Message Volume (Network Amplification) (The product does not sufficiently monitor or control transmitted network traffic volume, so that an actor can cause the product to transmit more traffic than should be allowed for that actor.).
How can I check Maven dependencies for CVE-2020-2100?
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-gpxv-776p-7gc7",
  "modified" : "2022-12-16T22:56:41Z",
  "published" : "2022-05-24T17:07:40Z",
  "aliases" : [ "CVE-2020-2100" ],
  "summary" : "Jenkins vulnerable to UDP amplification reflection attack",
  "details" : "Jenkins 2.218 and earlier, LTS 2.204.1 and earlier supports two network discovery services (UDP multicast/broadcast and DNS multicast) by default.\n\nThe UDP multicast/broadcast service can be used in an amplification reflection attack, as very few bytes sent to the respective endpoint result in much larger responses: A single byte request to this service would respond with more than 100 bytes of Jenkins metadata which could be used in a DDoS attack on a Jenkins controller. Within the same network, spoofed UDP packets could also be sent to make two Jenkins controllers go into an infinite loop of replies to one another, thus causing a denial of service.\n\nJenkins 2.219, LTS 2.204.2 now disables both UDP multicast/broadcast and DNS multicast by default.\n\nAdministrators that need these features can re-enable them again by setting the system property `hudson.DNSMultiCast.disabled` to `false` (for DNS multicast) or the system property `hudson.udp` to `33848`, or another port (for UDP broadcast/multicast). These are the same system properties that controlled whether these features were enabled in the past, so any instances explicitly enabling these features by setting these system properties will continue to have them enabled.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L"
  } ],
  "affected" : [ {
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    },
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      "type" : "ECOSYSTEM",
      "events" : [ {
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      }, {
        "fixed" : "2.204.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
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      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-2100"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/jenkins/commit/cd28a6d9347228b03da0e45653e23032342c2a36"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHBA-2020:0402"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHBA-2020:0675"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2020:0681"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2020:0683"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jenkinsci/jenkins"
  }, {
    "type" : "WEB",
    "url" : "https://jenkins.io/security/advisory/2020-01-29/#SECURITY-1641"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2020/01/29/1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-406" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-12-16T22:56:41Z",
    "nvd_published_at" : "2020-01-29T16:15:00Z"
  }
}