CVE-2026-0871: Keycloak Server Private SPI Improper Access Control Allows Administrators Vulnerability

MODERATE
Advisory Identifier: GHSA-v4jw-m6rm-399h
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CVSS 4.9
CWE-284 CWE-266
Published
Advisory Summary

CVE-2026-0871 is a MODERATE (CVSS 4.9) improper access control allows administrators vulnerability (CWE-284: Improper Access Control) affecting Keycloak Server Private SPI libraries in the Maven ecosystem. The issue involves improper access control allows administrators to bypass attribute visibility restrictions and modify unmanaged user profile attributes. Remediation is available by upgrading affected packages to version 26.5.2.

CVE-2026-0871 at a Glance

CVE Identifier CVE-2026-0871
GHSA Identifier GHSA-v4jw-m6rm-399h
Severity MODERATE
CVSS v3.1 Base Score 4.9
CWE Classification CWE-284: Improper Access Control
Affected Product Keycloak Server Private SPI
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.9

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

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

How to Fix CVE-2026-0871

To remediate this vulnerability, upgrade all affected Keycloak Server Private SPI 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-server-spi-private fixed: 26.5.2 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-server-spi-private</artifactId>
    <version>26.5.2</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-2026-0871, 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 Server Private SPI in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.5.2), 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-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Keycloak Server Private SPI, 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. An administrator with `manage-users` permission can bypass the "Only administrators can view" setting for unmanaged attributes, allowing them to modify these attributes. This improper access control can lead to unauthorized changes to user profiles, even when the system is configured to restrict such modifications.

CVE-2026-0871 Affected Keycloak Server Private SPI Versions

1 component(s)
Fixed Versions:
26.5.2
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-server-spi-private
maven/org.keycloak/keycloak-server-spi-private
Maven
< 26.5.2
26.5.2

References

NVD — CVE-2026-0871 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-0871
Keycloak Server Private SPI Source Repository REPOSITORY
https://github.com/keycloak/keycloak/issues/45873
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/9d0f679ecea405958f167fcd0f4a6db6ae32c3fa
access.redhat.com/errata/rhsa-2026:23... WEB
https://access.redhat.com/errata/RHSA-2026:2365
access.redhat.com/errata/rhsa-2026:23... WEB
https://access.redhat.com/errata/RHSA-2026:2366
Keycloak Server Private SPI Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-0871
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2428881
Keycloak Server Private SPI Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2026-0871?
CVE-2026-0871 is a security vulnerability in Keycloak Server Private SPI involving Improper Access Control Allows Administrators to Bypass Attribute Visibility Restrictions and Modify Unmanaged User Profile Attributes under CWE-284: Improper Access Control.
Which Keycloak Server Private SPI versions are affected?
Affected versions include releases prior to 26.5.2 across affected packages: org.keycloak:keycloak-server-spi-private.
What version fixes CVE-2026-0871?
Upgrading to 26.5.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-server-spi-private affected?
Yes, org.keycloak:keycloak-server-spi-private is affected in releases prior to 26.5.2. Upgrade your dependency to 26.5.2 or later.
What is the CVSS score of CVE-2026-0871?
CVE-2026-0871 has a CVSS v3.1 base score of 4.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2026-0871?
CVE-2026-0871 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check Maven dependencies for CVE-2026-0871?
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-v4jw-m6rm-399h",
  "modified" : "2026-02-28T02:42:55Z",
  "published" : "2026-02-27T09:30:29Z",
  "aliases" : [ "CVE-2026-0871" ],
  "summary" : "Keycloak Server Private SPI: Improper Access Control Allows Administrators to Bypass Attribute Visibility Restrictions and Modify Unmanaged User Profile Attributes",
  "details" : "A flaw was found in Keycloak. An administrator with `manage-users` permission can bypass the \"Only administrators can view\" setting for unmanaged attributes, allowing them to modify these attributes. This improper access control can lead to unauthorized changes to user profiles, even when the system is configured to restrict such modifications.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-server-spi-private"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-0871"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/issues/45873"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/9d0f679ecea405958f167fcd0f4a6db6ae32c3fa"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:2365"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:2366"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-0871"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2428881"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-266", "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-28T02:42:55Z",
    "nvd_published_at" : "2026-02-27T08:17:09Z"
  }
}