{"id":"BIT-keycloak-2026-18209","summary":"Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check","details":"A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows. The issue occurs because the security check designed to prevent HTTP parameter pollution only inspects the query portion of a redirect URL and ignores the fragment portion. When a client is configured with a wildcard redirect URI, an attacker can use this to inject duplicate security parameters into the login response. If a client application is not configured correctly, it might trust the attacker's injected data instead of the real security information from Keycloak, leading to session fixation or account confusion.","aliases":["CVE-2026-18209"],"modified":"2026-09-17T14:45:11.101645029Z","published":"2026-08-31T14:37:13.148Z","database_specific":{"severity":"Medium","cpes":["cpe:2.3:a:redhat:build_of_keycloak:*:*:*:*:-:*:*:*","cpe:2.3:a:keycloak:keycloak:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-18209"},{"type":"ADVISORY","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2508305"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-18209"},{"type":"WEB","url":"https://access.redhat.com/errata/RHSA-2026:68277"},{"type":"WEB","url":"https://access.redhat.com/errata/RHSA-2026:68278"}],"affected":[{"package":{"name":"keycloak","ecosystem":"Bitnami","purl":"pkg:bitnami/keycloak"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"26.7.3"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/keycloak/BIT-keycloak-2026-18209.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N"}]}],"schema_version":"1.9.0"}