CVE-2021-3827: Keycloak saml core ECP SAML Binding Bypasses Authentication Vulnerability

HIGH
Advisory Identifier: GHSA-4pc7-vqv5-5r3v
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CVSS 8.1
CWE-287
Published
Advisory Summary

CVE-2021-3827 is a HIGH (CVSS 8.1) ecp saml binding bypasses authentication vulnerability (CWE-287: Improper Authentication) affecting Keycloak saml core libraries in the Maven ecosystem. The issue involves ecp saml binding bypasses authentication flows. Remediation is available by upgrading affected packages to version 18.0.0.

CVE-2021-3827 at a Glance

CVE Identifier CVE-2021-3827
GHSA Identifier GHSA-4pc7-vqv5-5r3v
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-287: Improper Authentication
Affected Product Keycloak saml core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.1

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:H/I:H/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 High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2021-3827

To remediate this vulnerability, upgrade all affected Keycloak saml 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-saml-core fixed: 18.0.0 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-saml-core</artifactId>
    <version>18.0.0</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-2021-3827, 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 saml core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 18.0.0), 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-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In Keycloak saml 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

### Description A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

CVE-2021-3827 Affected Keycloak saml core Versions

1 component(s)
Fixed Versions:
18.0.0
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-saml-core
maven/org.keycloak/keycloak-saml-core
Maven
< 18.0.0
18.0.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/keycloak/keycloak/security/advisories/GHSA-4pc7-vqv5-5r3v
NVD — CVE-2021-3827 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3827
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/44000caaf5051d7f218d1ad79573bd3d175cad0d
Keycloak saml core Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2021-3827
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2007512
Keycloak saml core Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2021-3827?
CVE-2021-3827 is a security vulnerability in Keycloak saml core involving ECP SAML binding bypasses authentication flows under CWE-287: Improper Authentication.
Which Keycloak saml core versions are affected?
Affected versions include releases prior to 18.0.0 across affected packages: org.keycloak:keycloak-saml-core.
What version fixes CVE-2021-3827?
Upgrading to 18.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-saml-core affected?
Yes, org.keycloak:keycloak-saml-core is affected in releases prior to 18.0.0. Upgrade your dependency to 18.0.0 or later.
What is the CVSS score of CVE-2021-3827?
CVE-2021-3827 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2021-3827?
CVE-2021-3827 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check Maven dependencies for CVE-2021-3827?
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-4pc7-vqv5-5r3v",
  "modified" : "2022-12-01T22:10:45Z",
  "published" : "2022-04-27T21:25:59Z",
  "aliases" : [ "CVE-2021-3827" ],
  "summary" : "ECP SAML binding bypasses authentication flows",
  "details" : "### Description\nA flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-saml-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "18.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/security/advisories/GHSA-4pc7-vqv5-5r3v"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3827"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/44000caaf5051d7f218d1ad79573bd3d175cad0d"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2021-3827"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2007512"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-04-27T21:25:59Z",
    "nvd_published_at" : "2022-08-23T16:15:00Z"
  }
}