Group Policy Evaluation Flaw in Keycloak by Red Hat
CVE-2026-18203

6.5MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Build Of Keycloak
Red Hat Data Grid 8
Red Hat Jboss Enterprise Application Platform Expansion Pack
Red Hat Single Sign-on 7
Vendor
CVE Published:
31 July 2026

What is CVE-2026-18203?

A vulnerability in Keycloak's group policy evaluation logic allows users to bypass security checks through an inadequate prefix-based check for group membership. Specifically, when extending permissions to child groups, the system erroneously allows users from groups with similar names to gain unauthorized access to sensitive administrative functions. This improper validation can lead to potential misuse of protected resources, highlighting the need for enhanced security measures.

References

https://access.redhat.com/security/cve/CVE-2026-18203
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2508291
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Red Hat would like to thank Paul Bottinelli (Trail of Bits) for reporting this issue.
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