A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00203.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Red Hat Red Hat Build of Keycloak affected —
Red Hat Red Hat Build of Keycloak affected —
Red Hat Red Hat Build of Keycloak affected —
Red Hat Red Hat Data Grid 8 unaffected —
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack unaffected —
Red Hat Red Hat Single Sign-On 7 unaffected —

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Project Subscriptions

Vendors Products
Redhat Subscribe
Build Keycloak Subscribe
Jboss Data Grid Subscribe
Jbosseapxp Subscribe
Red Hat Single Sign On Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

References
Link Providers
https://access.redhat.com/security/cve/CVE-2026-18203 cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2508291 cve-icon
History

Fri, 31 Jul 2026 07:30:00 +0000

Type Values Removed Values Added
Description A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.
Title Keycloak-services: keycloak-services: group policy extendchildren matches sibling group path prefixes
First Time appeared Redhat
Redhat build Keycloak
Redhat jboss Data Grid
Redhat jbosseapxp
Redhat red Hat Single Sign On
Weaknesses CWE-863
CPEs cpe:/a:redhat:build_keycloak:
cpe:/a:redhat:jboss_data_grid:8
cpe:/a:redhat:jbosseapxp
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
Redhat build Keycloak
Redhat jboss Data Grid
Redhat jbosseapxp
Redhat red Hat Single Sign On
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-07-31T07:08:26.588Z

Reserved: 2026-07-29T07:49:19.596Z

Link: CVE-2026-18203

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-07-31T18:45:04Z

Weaknesses