CVE-2021-20195: Keycloak core Cross-Site Scripting Vulnerability

CRITICAL
Advisory Identifier: GHSA-q6w2-89hq-hq27
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CVSS 9.6
CWE-116 CWE-20 CWE-79
Published
Advisory Summary

CVE-2021-20195 is a CRITICAL (CVSS 9.6) cross-site scripting vulnerability (CWE-116: Improper Encoding or Escaping of Output) affecting Keycloak core libraries in the Maven ecosystem. The issue involves keycloak self stored cross-site scripting vulnerability. Remediation is available by upgrading affected packages to version 13.0.0.

CVE-2021-20195 at a Glance

CVE Identifier CVE-2021-20195
GHSA Identifier GHSA-q6w2-89hq-hq27
Severity CRITICAL
CVSS v3.1 Base Score 9.6
CWE Classification CWE-116: Improper Encoding or Escaping of Output
Affected Product Keycloak core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.6

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:R/S:C/C:H/I:H/A:H).

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

How to Fix CVE-2021-20195

To remediate this vulnerability, upgrade all affected Keycloak 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.keycloak:keycloak-core fixed: 13.0.0 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-core</artifactId>
    <version>13.0.0</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.keycloak

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-20195, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.keycloak

Analyze the terminal output to locate any version of Keycloak core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 13.0.0), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.keycloak 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-116: Improper Encoding or Escaping of Output, where the product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. as a result, the intended structure of the message is not preserved. In Keycloak 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

A flaw was found in keycloak in versions before 13.0.0. A Self Stored XSS attack vector escalating to a complete account takeover is possible due to user-supplied data fields not being properly encoded and Javascript code being used to process the data. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

CVE-2021-20195 Affected Keycloak core Versions

1 component(s)
Fixed Versions:
13.0.0
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-core
maven/org.keycloak/keycloak-core
Maven
< 13.0.0
13.0.0

References

NVD — CVE-2021-20195 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-20195
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/717d9515fa131e3d8c8936e41b2e52270fdec976
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1919143

Frequently Asked Questions

What is CVE-2021-20195?
CVE-2021-20195 is a security vulnerability in Keycloak core involving keycloak Self Stored Cross-site Scripting vulnerability under CWE-116: Improper Encoding or Escaping of Output.
Which Keycloak core versions are affected?
Affected versions include releases prior to 13.0.0 across affected packages: org.keycloak:keycloak-core.
What version fixes CVE-2021-20195?
Upgrading to 13.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-core affected?
Yes, org.keycloak:keycloak-core is affected in releases prior to 13.0.0. Upgrade your dependency to 13.0.0 or later.
What is the CVSS score of CVE-2021-20195?
CVE-2021-20195 has a CVSS v3.1 base score of 9.6 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.
What CWE is associated with CVE-2021-20195?
CVE-2021-20195 is classified under CWE-116: Improper Encoding or Escaping of Output (The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.).
How can I check Maven dependencies for CVE-2021-20195?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.keycloak'. 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-q6w2-89hq-hq27",
  "modified" : "2022-08-11T16:52:01Z",
  "published" : "2021-06-08T23:02:43Z",
  "aliases" : [ "CVE-2021-20195" ],
  "summary" : "keycloak Self Stored Cross-site Scripting vulnerability",
  "details" : "A flaw was found in keycloak in versions before 13.0.0. A Self Stored XSS attack vector escalating to a complete account takeover is possible due to user-supplied data fields not being properly encoded and Javascript code being used to process the data. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "13.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-20195"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/717d9515fa131e3d8c8936e41b2e52270fdec976"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1919143"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-20", "CWE-79" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-06-01T17:55:29Z",
    "nvd_published_at" : "2021-05-28T11:15:00Z"
  }
}