CVE-2026-18214: Keycloak-services: keycloak-services: google external access-token exchange bypasses hosted-domain restriction

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-31 · updated 2026-09-16
Weakness: CWE-862

Description

Keycloak allows users to log in using Google accounts and can be configured to only allow users from specific Google Workspace domains. A flaw was found where the token exchange feature, which allows swapping a Google token for a Keycloak token, does not check these domain restrictions. This means an attacker with a valid Google account from a different domain could bypass the security check and gain access to the Keycloak realm.

Affected products

Red Hat build of Keycloak 26.4: all versions

References

https://access.redhat.com/errata/RHSA-2026:68277
https://access.redhat.com/errata/RHSA-2026:68278
https://access.redhat.com/security/cve/CVE-2026-18214
https://bugzilla.redhat.com/show_bug.cgi?id=2508308

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