CVE-2021-3856: Keycloak core Keycloak Has Files Or Directories Vulnerability

MODERATE
Advisory Identifier: GHSA-3w4v-rvc4-2xpw
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CVSS 4.3
CWE-552 CWE-22
Published
Advisory Summary

CVE-2021-3856 is a MODERATE (CVSS 4.3) keycloak has files or directories vulnerability (CWE-552: Files or Directories Accessible to External Parties) affecting Keycloak core libraries in the Maven ecosystem. The issue involves keycloak has files or directories accessible to external parties. Remediation is available by upgrading affected packages to version 15.1.0.

CVE-2021-3856 at a Glance

CVE Identifier CVE-2021-3856
GHSA Identifier GHSA-3w4v-rvc4-2xpw
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-552: Files or Directories Accessible to External Parties
Affected Product Keycloak core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.3

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

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

How to Fix CVE-2021-3856

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: 15.1.0 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-core</artifactId>
    <version>15.1.0</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-2021-3856, 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 15.1.0), 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-552: Files or Directories Accessible to External Parties, where the product makes files or directories accessible to unauthorized actors, even though they should not be. 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

ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader. By sending requests for theme resources with a relative path from an external HTTP client, the client will receive the content of random files if available.

CVE-2021-3856 Affected Keycloak core Versions

1 component(s)
Fixed Versions:
15.1.0
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-core
maven/org.keycloak/keycloak-core
Maven
< 15.1.0
15.1.0

References

NVD — CVE-2021-3856 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3856
Keycloak core Source Repository REPOSITORY
https://github.com/keycloak/keycloak/pull/8588
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/73f0474008e1bebd0733e62a22aceda9e5de6743
Keycloak core Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2021-3856
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2010164
Keycloak core Source Repository REPOSITORY
https://github.com/keycloak/keycloak
issues.redhat.com/browse/keycloak-194... WEB
https://issues.redhat.com/browse/KEYCLOAK-19422

Frequently Asked Questions

What is CVE-2021-3856?
CVE-2021-3856 is a security vulnerability in Keycloak core involving Keycloak has Files or Directories Accessible to External Parties under CWE-552: Files or Directories Accessible to External Parties.
Which Keycloak core versions are affected?
Affected versions include releases prior to 15.1.0 across affected packages: org.keycloak:keycloak-core.
What version fixes CVE-2021-3856?
Upgrading to 15.1.0 (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 15.1.0. Upgrade your dependency to 15.1.0 or later.
What is the CVSS score of CVE-2021-3856?
CVE-2021-3856 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2021-3856?
CVE-2021-3856 is classified under CWE-552: Files or Directories Accessible to External Parties (The product makes files or directories accessible to unauthorized actors, even though they should not be.).
How can I check Maven dependencies for CVE-2021-3856?
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-3w4v-rvc4-2xpw",
  "modified" : "2022-09-02T21:12:52Z",
  "published" : "2022-08-27T00:00:45Z",
  "aliases" : [ "CVE-2021-3856" ],
  "summary" : "Keycloak has Files or Directories Accessible to External Parties",
  "details" : "ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader. By sending requests for theme resources with a relative path from an external HTTP client, the client will receive the content of random files if available.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "15.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3856"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/pull/8588"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/73f0474008e1bebd0733e62a22aceda9e5de6743"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2021-3856"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2010164"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  }, {
    "type" : "WEB",
    "url" : "https://issues.redhat.com/browse/KEYCLOAK-19422"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-552" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-09-02T21:12:52Z",
    "nvd_published_at" : "2022-08-26T16:15:00Z"
  }
}