Quick answers
- Is CVE-2026-18208 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18208 being exploited in the wild.
- How severe is CVE-2026-18208?
- Medium severity, with a CVSS score of 6.5, published 31 July 2026.
- Which products and versions are affected?
- Keycloak All versions.
- Is there a fix for CVE-2026-18208?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-18208 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-18208?
- Check whether you run Keycloak at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A vulnerability exists in the OIDC token introspection endpoint within the keycloak-services component. When a confidential client is configured to receive signed JWT introspection responses (client.introspection.response.allow.jwt.claim.enabled set to true), the server fails to sanitize the 'jwt' field in the response for out-of-audience tokens. While the endpoint correctly marks the token as 'active: false', it still includes the full set of token claims within the signed JWT field. An attacker controlling a confidential client can exploit this to bypass audience-based restrictions and recover sensitive identity information, such as roles and user attributes, from tokens intended for other clients. This is identified as an incomplete fix for a previous vulnerability.
Affected products
- Red Hat Build of Keycloak All versions
- Keycloak Keycloak All versions
Timeline
- 2026-07-29: disclosed: Initial report in Red Hat Bugzilla
- 2026-07-31: advisory: NVD publication date