Security Flaw in Keycloak Services Affects Token Introspection Process
CVE-2026-18208

6.5MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Build Of Keycloak
Red Hat Data Grid 8
Red Hat Jboss Enterprise Application Platform Expansion Pack
Red Hat Single Sign-on 7
Vendor
CVE Published:
31 July 2026

What is CVE-2026-18208?

A vulnerability exists in the OIDC token introspection endpoint of the Keycloak services component, which is critical for managing access and securing applications. This flaw occurs when a confidential client, tasked with handling signed JWT introspection responses, introspects a token meant for a different audience. Although the system recognizes the token as inactive, it still discloses the full token claims within a signed JWT payload. Consequently, this allows unauthorized clients to circumvent audience-based restrictions, leading to the potential exposure of sensitive information contained within the token.

References

https://access.redhat.com/security/cve/CVE-2026-18208
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2508304
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Red Hat would like to thank Paul Bottinelli (Trail of Bits) for reporting this issue.
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