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Fencer Vulns
medium 6.5

CVE-2026-18208 json

Keycloak-services: keycloak-services: inactive out-of-audience token introspection leaks signed jwt claim

published 2026-07-31 3 mo ago modified 2026-11-06 2 d ago also EUVD-2026-51482

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

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.

Patch / fix

  • Red Hat Red Hat build of Keycloak 26.6 26.6-24, 26.6.8-2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-18208 updated cvss 6.5

keycloak-services: keycloak-services: Inactive out-of-audience token introspection leaks signed JWT claim

  • Red Hat Build of Keycloak rhbk-keycloak-rhel9, keycloak-services 26.6.4.redhat-00004
    affected: workaround, no fix available “Fix deferred”
  • Red Hat build of Keycloak 26.6 rhbk/keycloak-rhel9 26.6-24, rhbk/keycloak-rhel9-operator 26.6-24, rhbk/keycloak-operator-bundle 26.6.8-2
    fixed: vendor fix RHSA-2026:95762
  • Red Hat build of Keycloak 26.6.8
    fixed: vendor fix RHSA-2026:95761
  • Red Hat Data Grid 8 keycloak-services 26.6.4.redhat-00004 Red Hat JBoss Enterprise Application Platform Expansion Pack keycloak-services 26.6.4.redhat-00004 Red Hat Single Sign-On 7 keycloak-services 26.6.4.redhat-00004
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Affected products

  • Red Hat Red Hat build of Keycloak 26.6
  • Red Hat Red Hat build of Keycloak 26.6.8
  • Red Hat Red Hat Build of Keycloak
  • Red Hat Red Hat Data Grid 8
  • Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack
  • Red Hat Red Hat Single Sign-On 7

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.