CVE-2026-3872: Keycloak Path Traversal Vulnerability

HIGH
Advisory Identifier: GHSA-cjm2-j6cm-6p6m
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CVSS 7.3
CWE-601
Published
Advisory Summary

CVE-2026-3872 is a HIGH (CVSS 7.3) path traversal vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Keycloak libraries in the Maven ecosystem. The issue involves redirect uri validation bypass via ..;/ path traversal in oidc auth endpoint. Remediation is available by upgrading affected packages to version 26.5.7.

CVE-2026-3872 at a Glance

CVE Identifier CVE-2026-3872
GHSA Identifier GHSA-cjm2-j6cm-6p6m
Severity HIGH
CVSS v3.1 Base Score 7.3
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Keycloak
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.3

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:R/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 Required (UI:R)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-3872

To remediate this vulnerability, upgrade all affected Keycloak 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-services fixed: 26.5.7 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-services</artifactId>
    <version>26.5.7</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-2026-3872, 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 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.5.7), 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-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Keycloak, 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. This issue allows an attacker, who controls another path on the same web server, to bypass the allowed path in redirect Uniform Resource Identifiers (URIs) that use a wildcard. A successful attack may lead to the theft of an access token, resulting in information disclosure.

CVE-2026-3872 Affected Keycloak Versions

1 component(s)
Fixed Versions:
26.5.7
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-services
maven/org.keycloak/keycloak-services
Maven
< 26.5.7
26.5.7

References

NVD — CVE-2026-3872 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3872
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak/issues/47718
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/35a71b00bc856ac402711130f60190d3a24795e7
access.redhat.com/errata/rhsa-2026:64... WEB
https://access.redhat.com/errata/RHSA-2026:6475
access.redhat.com/errata/rhsa-2026:64... WEB
https://access.redhat.com/errata/RHSA-2026:6476
access.redhat.com/errata/rhsa-2026:64... WEB
https://access.redhat.com/errata/RHSA-2026:6477
access.redhat.com/errata/rhsa-2026:64... WEB
https://access.redhat.com/errata/RHSA-2026:6478
Keycloak Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-3872
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2445988
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2026-3872?
CVE-2026-3872 is a security vulnerability in Keycloak involving Redirect URI validation bypass via ..;/ path traversal in OIDC auth endpoint under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Keycloak versions are affected?
Affected versions include releases prior to 26.5.7 across affected packages: org.keycloak:keycloak-services.
What version fixes CVE-2026-3872?
Upgrading to 26.5.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-services affected?
Yes, org.keycloak:keycloak-services is affected in releases prior to 26.5.7. Upgrade your dependency to 26.5.7 or later.
What is the CVSS score of CVE-2026-3872?
CVE-2026-3872 has a CVSS v3.1 base score of 7.3 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-3872?
CVE-2026-3872 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check Maven dependencies for CVE-2026-3872?
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-cjm2-j6cm-6p6m",
  "modified" : "2026-04-04T05:59:35Z",
  "published" : "2026-04-02T15:31:38Z",
  "aliases" : [ "CVE-2026-3872" ],
  "summary" : "Keycloak: Redirect URI validation bypass via ..;/ path traversal in OIDC auth endpoint",
  "details" : "A flaw was found in Keycloak. This issue allows an attacker, who controls another path on the same web server, to bypass the allowed path in redirect Uniform Resource Identifiers (URIs) that use a wildcard. A successful attack may lead to the theft of an access token, resulting in information disclosure.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-services"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-3872"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/issues/47718"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/35a71b00bc856ac402711130f60190d3a24795e7"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:6475"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:6476"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:6477"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:6478"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-3872"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2445988"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-04T05:59:35Z",
    "nvd_published_at" : "2026-04-02T13:16:26Z"
  }
}