CVE-2026-18211 Keycloak-services: keycloak-services: secure-client-uris policy bypass via localhost-prefixed domains
Attackers can bypass secure-client-uris policies using crafted domains to intercept authentication codes over unencrypted connections in Keycloak.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-18211?
CVE-2026-18211 is a medium-severity vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
A flaw was found in the secure-client-uris client policy executor within Keycloak core services. This component is responsible for enforcing security requirements on client configurations, such as requiring encrypted connections for redirect URIs. Due to an improper check that only looks at the start of a web address rather than properly verifying the host, an attacker can bypass these security restrictions by using a specially crafted domain name. This could allow an attacker to intercept sensitive authentication codes over unencrypted connections.
Weakness: CWE-20
Which versions are affected by CVE-2026-18211?
It affects 1 product.
Products include Redhat Build of Keycloak.
How do I fix CVE-2026-18211?
No fix has been published for CVE-2026-18211 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-18211 being exploited?
There is no known exploitation of CVE-2026-18211 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-6j79-4gfx-fm6f.