CVE-2020-2102: Jenkins core Non-constant Time HMAC Comparison Vulnerability

MODERATE
Advisory Identifier: GHSA-fj6f-6933-839j
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CVSS 5.3
CWE-203 CWE-208
Published
Advisory Summary

CVE-2020-2102 is a MODERATE (CVSS 5.3) non-constant time hmac comparison vulnerability (CWE-203: Observable Discrepancy) affecting Jenkins core libraries in the Maven ecosystem. The issue involves non-constant time hmac comparison. Remediation is available by upgrading affected packages to version 2.204.2, 2.219.

CVE-2020-2102 at a Glance

CVE Identifier CVE-2020-2102
GHSA Identifier GHSA-fj6f-6933-839j
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-203: Observable Discrepancy
Affected Product Jenkins core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.3

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

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

How to Fix CVE-2020-2102

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-2020-2102, 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-203: Observable Discrepancy, where the product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized 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 does not use a constant-time comparison when checking whether two HMACs are equal. This could potentially allow attackers to use statistical methods to obtain a valid HMAC for an attacker-controlled input value. Jenkins 2.219, LTS 2.204.2 now uses a constant-time comparison when validating HMACs.

CVE-2020-2102 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-2020-2102 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-2102
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/jenkins/commit/6f35dbb939ebe947bdb1979010b208480f1d0e31
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-1660
Jenkins core Security Information SECURITY
http://www.openwall.com/lists/oss-security/2020/01/29/1

Frequently Asked Questions

What is CVE-2020-2102?
CVE-2020-2102 is a security vulnerability in Jenkins core involving Non-constant time HMAC comparison under CWE-203: Observable Discrepancy.
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-2020-2102?
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-2020-2102?
CVE-2020-2102 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2020-2102?
CVE-2020-2102 is classified under CWE-203: Observable Discrepancy (The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.).
How can I check Maven dependencies for CVE-2020-2102?
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-fj6f-6933-839j",
  "modified" : "2022-12-19T21:06:59Z",
  "published" : "2022-05-24T17:07:40Z",
  "aliases" : [ "CVE-2020-2102" ],
  "summary" : "Non-constant time HMAC comparison",
  "details" : "Jenkins 2.218 and earlier, LTS 2.204.1 and earlier does not use a constant-time comparison when checking whether two HMACs are equal. This could potentially allow attackers to use statistical methods to obtain a valid HMAC for an attacker-controlled input value.\n\nJenkins 2.219, LTS 2.204.2 now uses a constant-time comparison when validating HMACs.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.204.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.204.1"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.main:jenkins-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.205"
      }, {
        "fixed" : "2.219"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.218"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-2102"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/jenkins/commit/6f35dbb939ebe947bdb1979010b208480f1d0e31"
  }, {
    "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-1660"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2020/01/29/1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-203", "CWE-208" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-12-19T21:06:59Z",
    "nvd_published_at" : "2020-01-29T16:15:00Z"
  }
}