CVE-2026-18203 — MEDIUM (6.5)

Vulnerability 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.

CVSS Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

HIGH

Availability

NONE

Affected Products

Vendor	Product	Versions
Redhat	Build Of Keycloak	-

Related Weaknesses (CWE)

CWE-863

References

https://access.redhat.com/security/cve/CVE-2026-18203Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2508291Issue TrackingVendor Advisory

FAQ

What is CVE-2026-18203?

CVE-2026-18203 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 ...

How severe is CVE-2026-18203?

CVE-2026-18203 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-18203?

Check the references section above for vendor advisories and patch information. Affected products include: Redhat Build Of Keycloak.