# CVE-2026-18206: Keycloak-services: keycloak-services: client policy source-host wildcard domain matching bypass

Status: published. Published: 2026-07-31. Updated: 2026-11-07.

A flaw was found in the keycloak-services component of Keycloak, which provides identity and access management services. The issue occurs when a realm administrator uses a wildcard domain (like *.example.com) to restrict which hosts can register or update clients. Due to improper validation, the system accepts any hostname that ends with the specified domain suffix, even if it is not a legitimate subdomain. An attacker who can control the reverse DNS of their connection can bypass these host-based restrictions, potentially allowing unauthorized client modifications.

## Remediation

- 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. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat build of Keycloak 26.6 (rhbk/keycloak-operator-bundle): ≥ 26.6.8-2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat build of Keycloak 26.6 (rhbk/keycloak-rhel9): ≥ 26.6-24; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat build of Keycloak 26.6 (rhbk/keycloak-rhel9-operator): ≥ 26.6-24; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat build of Keycloak 26.6.8 (keycloak-services): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat build of Keycloak 26.6.8 (rhbk-keycloak-rhel9/rhbk-keycloak-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat build of Keycloak 26.6.8 (rhbk-openshift-rhel9/rhbk-openshift-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Data Grid 8 (keycloak-services): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat JBoss Enterprise Application Platform Expansion Pack (keycloak-services): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Single Sign-On 7 (keycloak-services): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 3.7 (low); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.32% as of 2026-11-06; percentile 24.68%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-20

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:95761 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:95762 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-18206 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2508292 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-18206; retrieved 2026-11-07; source updated 2026-11-07

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-18206; retrieved 2026-11-07; source updated Not reported

Revision: cea76f0abe4e10525f5c925c803dd75d52c66967daed2640b8066a045ea8ca38

Canonical: https://y2.dev/cve/CVE-2026-18206

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