A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

CWE-347

https://access.redhat.com/errata/RHSA-2026:30083

https://access.redhat.com/errata/RHSA-2026:30084

https://access.redhat.com/security/cve/CVE-2026-11800

https://bugzilla.redhat.com/show_bug.cgi?id=2487006

[{"vendor":"Red Hat","product":"Red Hat build of Keycloak 26.6","defaultStatus":"affected","collectionURL":"https://catalog.redhat.com/software/containers/","packageName":"rhbk/keycloak-operator-bundle","cpes":["cpe:/a:redhat:build_keycloak:26.6::el9"],"versions":[{"version":"26.6.4-2","lessThan":"*","versionType":"rpm","status":"unaffected"}]},{"vendor":"Red Hat","product":"Red Hat build of Keycloak 26.6","defaultStatus":"affected","collectionURL":"https://catalog.redhat.com/software/containers/","packageName":"rhbk/keycloak-rhel9","cpes":["cpe:/a:redhat:build_keycloak:26.6::el9"],"versions":[{"version":"26.6-8","lessThan":"*","versionType":"rpm","status":"unaffected"}]},{"vendor":"Red Hat","product":"Red Hat build of Keycloak 26.6","defaultStatus":"affected","collectionURL":"https://catalog.redhat.com/software/containers/","packageName":"rhbk/keycloak-rhel9-operator","cpes":["cpe:/a:redhat:build_keycloak:26.6::el9"],"versions":[{"version":"26.6-8","lessThan":"*","versionType":"rpm","status":"unaffected"}]},{"vendor":"Red Hat","product":"Red Hat build of Keycloak 26.6.4","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:build_keycloak:26.6::el9"]},{"vendor":"Red Hat","product":"Red Hat Build of Keycloak","defaultStatus":"affected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"rhbk/keycloak-rhel9","cpes":["cpe:/a:redhat:build_keycloak:"]},{"vendor":"Red Hat","product":"Red Hat Build of Keycloak","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"rhbk-openshift-rhel9/rhbk-openshift-rhel9","cpes":["cpe:/a:redhat:build_keycloak:"]},{"vendor":"Red Hat","product":"Red Hat Data Grid 8","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"keycloak-services","cpes":["cpe:/a:redhat:jboss_data_grid:8"]},{"vendor":"Red Hat","product":"Red Hat JBoss Enterprise Application Platform Expansion Pack","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/jbossnetwork/restricted/listSoftware.html","packageName":"keycloak-services","cpes":["cpe:/a:redhat:jbosseapxp"]},{"vendor":"Red Hat","product":"Red Hat Single Sign-On 7","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"keycloak-services","cpes":["cpe:/a:redhat:red_hat_single_sign_on:7"]}]