Keycloak-services: keycloak-services: group policy extendchildren matches sibling group path prefixes

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-18203
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-31 08:16:27 UTC
Updated2026-08-03 16:39:02 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

EPSS: 0.002030000 probability, percentile 0.103770000 (date 2026-08-05)

Problem Types: CWE-863 | CWE-863 Incorrect Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
3.1CNACVSS6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Build Of Keycloak Not specified Not specified
CNA Red Hat Red Hat Build Of Keycloak Not specified Not specified
CNA Red Hat Red Hat Build Of Keycloak Not specified Not specified
CNA Red Hat Red Hat Data Grid 8 Not specified Not specified
CNA Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack Not specified Not specified
CNA Red Hat Red Hat Single Sign-On 7 Not specified Not specified

References

ReferenceSourceLinkTags
access.redhat.com/security/cve/CVE-2026-18203 [email protected] access.redhat.com
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

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

Additional Advisory Data

SourceTimeEvent
CNA2026-07-28T13:44:55.000ZReported to Red Hat.
CNA2026-07-28T13:44:55.000ZMade public.

Workarounds

CNA: 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.

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