CVE-2026-18208 Keycloak-services: keycloak-services: inactive out-of-audience token introspection leaks signed jwt claim
An attacker can bypass audience restrictions to read sensitive token claims via the OIDC introspection endpoint in Keycloak.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-18208?
CVE-2026-18208 is a medium-severity vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
A flaw was found in the OIDC token introspection endpoint of the keycloak-services component. Keycloak is an open-source identity and access management solution used to secure modern applications and services. The issue occurs when a confidential client, configured to receive signed JWT introspection responses, attempts to introspect a token issued for a different audience. Although the endpoint correctly identifies the token as inactive for that client, it still returns the full set of token claims within a signed JWT field. This allows an unauthorized client to bypass audience-based restrictions and access sensitive information contained in the token.
Weakness: CWE-862
Which versions are affected by CVE-2026-18208?
It affects 1 product.
Products include Redhat Build of Keycloak.
How do I fix CVE-2026-18208?
No fix has been published for CVE-2026-18208 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-18208 being exploited?
There is no known exploitation of CVE-2026-18208 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-jg59-c35g-76r8.