Bug 2508308 (CVE-2026-18214)

Summary:	CVE-2026-18214 keycloak-services: keycloak-services: Google external access-token exchange bypasses hosted-domain restriction
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	anujha, aschwart, asoldano, aszczucz, bbaranow, bmaxwell, boliveir, bstansbe, dlofthou, drichtar, istudens, ivassile, iweiss, mosmerov, mposolda, msvehla, nwallace, pberan, pesilva, pjindal, pmackay, rmartinc, rstancel, ssilvert, sthorger, thjenkin, vdosoudi, vmuzikar
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	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.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-29 08:40:56 UTC

A Missing Authorization vulnerability was identified in Keycloak Google Identity Provider implementation. The flaw exists in the external access-token exchange code path, which is used when the Token Exchange V1 feature is enabled.
While the standard Google ID-token login flow correctly validates the hd hosted domain claim against the configured hostedDomain setting, the access-token exchange flow skips this validation. When an external access token is provided, Keycloak retrieves the user profile from the Google user-info endpoint but fails to verify that the domain associated with the user matches the restricted domain configured in the Identity Provider settings.
An attacker with a valid Google access token for any domain can exploit this flaw if they have access to a confidential client authorized to perform token exchange. Successful exploitation allows the attacker to bypass domain restrictions, obtain a Keycloak access token, and potentially create or link a brokered identity that should have been restricted.