CVE-2026-18206 Keycloak-services: keycloak-services: client policy source-host wildcard domain matching bypass
Attackers can bypass client registration restrictions by exploiting improper wildcard domain validation in Keycloak, allowing unauthorized client modifications.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-18206?
CVE-2026-18206 is a low-severity vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-20
Which versions are affected by CVE-2026-18206?
It affects 1 product.
Products include Redhat Build of Keycloak.
How do I fix CVE-2026-18206?
No fix has been published for CVE-2026-18206 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-18206 being exploited?
There is no known exploitation of CVE-2026-18206 in the wild and no public exploit code.
Other vulnerabilities in Redhat Build of Keycloak
- CVE-2026-15572 Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation
- CVE-2026-3047 Keycloak SAML Broken has Authentication Bypass by Primary Weakness
- CVE-2026-15573 Keycloak-services: keycloak-services: authorization bypass via unnormalized uri matching in pathmatcher
- CVE-2026-16102 Keycloak-services: keycloak-services: default dcr policy allows role forgery via user property mappers
- CVE-2026-1609 Org.keycloak/keycloak-quarkus-server: keycloak: unauthorized access via jwt authorization grant with disabled users
Sources
Also known as GHSA-2w88-g477-cxmj.