CVE-2021-21658: Nuget XML External Entity Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-p674-hh8x-rv5h
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CVSS 9.1
CWE-611
Published
Advisory Summary

CVE-2021-21658 is a CRITICAL (CVSS 9.1) xml external entity vulnerability vulnerability (CWE-611: Improper Restriction of XML External Entity Reference) affecting Nuget libraries in the Maven ecosystem. The issue involves xml external entity vulnerability in jenkins nuget plugin. Remediation is available by upgrading affected packages to version 1.1.

CVE-2021-21658 at a Glance

CVE Identifier CVE-2021-21658
GHSA Identifier GHSA-p674-hh8x-rv5h
Severity CRITICAL
CVSS v3.1 Base Score 9.1
CWE Classification CWE-611: Improper Restriction of XML External Entity Reference
Affected Product Nuget
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.1

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

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

How to Fix CVE-2021-21658

To remediate this vulnerability, upgrade all affected Nuget 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.plugins:nuget fixed: 1.1 
<dependency>
    <groupId>org.jenkins-ci.plugins</groupId>
    <artifactId>nuget</artifactId>
    <version>1.1</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.plugins

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-21658, inspect your build dependencies using the Maven Dependency Plugin:

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

Analyze the terminal output to locate any version of Nuget in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.1), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.jenkins-ci.plugins 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-611: Improper Restriction of XML External Entity Reference, where the product processes an xml document that can contain xml entities with uris that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output. In Nuget, 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 Nuget Plugin 1.0 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks. This XML parser is used for the \"Build on NuGet updates\" feature. This allows attackers with the ability to control the contents of the `packages.config` file in a workspace to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the Jenkins controller or server-side request forgery. Jenkins Nuget Plugin 1.1 disables external entity resolution for its XML parser.

CVE-2021-21658 Affected Nuget Versions

1 component(s)
Fixed Versions:
1.1
Product / Package Ecosystem Affected Versions Fixed Version
org.jenkins-ci.plugins:nuget
maven/org.jenkins-ci.plugins/nuget
Maven
< 1.1
1.1

References

NVD — CVE-2021-21658 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21658
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/nuget-plugin/commit/542bf38ac52f045741a5670e1644af351878f7e0
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/nuget-plugin/commit/c8ed4cb5b1c42f3c407f9f418b4e0b4274bea5a9
Nuget Source Repository REPOSITORY
https://github.com/jenkinsci/nuget-plugin
Nuget Security Information SECURITY
https://www.jenkins.io/security/advisory/2021-05-25/#SECURITY-2340
Nuget Security Information SECURITY
http://www.openwall.com/lists/oss-security/2021/05/25/3

Frequently Asked Questions

What is CVE-2021-21658?
CVE-2021-21658 is a security vulnerability in Nuget involving XML external entity vulnerability in Jenkins Nuget Plugin under CWE-611: Improper Restriction of XML External Entity Reference.
Which Nuget versions are affected?
Affected versions include releases prior to 1.1 across affected packages: org.jenkins-ci.plugins:nuget.
What version fixes CVE-2021-21658?
Upgrading to 1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nuget affected?
Yes, org.jenkins-ci.plugins:nuget is affected in releases prior to 1.1. Upgrade your dependency to 1.1 or later.
What is the CVSS score of CVE-2021-21658?
CVE-2021-21658 has a CVSS v3.1 base score of 9.1 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2021-21658?
CVE-2021-21658 is classified under CWE-611: Improper Restriction of XML External Entity Reference (The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.).
How can I check Maven dependencies for CVE-2021-21658?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.jenkins-ci.plugins'. 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-p674-hh8x-rv5h",
  "modified" : "2023-10-27T15:00:45Z",
  "published" : "2022-05-24T19:03:11Z",
  "aliases" : [ "CVE-2021-21658" ],
  "summary" : "XML external entity vulnerability in Jenkins Nuget Plugin",
  "details" : "Jenkins Nuget Plugin 1.0 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks. This XML parser is used for the \\\"Build on NuGet updates\\\" feature.\n\nThis allows attackers with the ability to control the contents of the `packages.config` file in a workspace to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the Jenkins controller or server-side request forgery.\n\nJenkins Nuget Plugin 1.1 disables external entity resolution for its XML parser.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.plugins:nuget"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-21658"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/nuget-plugin/commit/542bf38ac52f045741a5670e1644af351878f7e0"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/nuget-plugin/commit/c8ed4cb5b1c42f3c407f9f418b4e0b4274bea5a9"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jenkinsci/nuget-plugin"
  }, {
    "type" : "WEB",
    "url" : "https://www.jenkins.io/security/advisory/2021-05-25/#SECURITY-2340"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2021/05/25/3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-611" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-09-07T23:54:54Z",
    "nvd_published_at" : "2021-05-25T17:15:00Z"
  }
}