CVE-2026-18208 Keycloak-services: keycloak-services: inactive out-of-audience token introspection leaks signed jwt claim
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.
CVSS 3.1 detail
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:NExploitable remotely over the network, with an ordinary account and without any user action; an attacker can seriously compromise confidentiality, integrity or availability.
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- Interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Red Hat Build of Keycloak | Versions not published | |
| Red Hat Data Grid 8 | Versions not published | |
| Red Hat JBoss Enterprise Application Platform Expansion Pack | Versions not published | |
| Red Hat Single Sign-On 7 | Versions not published | |
| Red Hat build of Keycloak 26.6.8 | Versions not published | |
| Red Hat build of Keycloak 26.6 26.6 | earliest → < 26.6-24 | 26.6-24 |