{"id":"CVE-2026-18209","aliases":["BIT-keycloak-2026-18209","EUVD-2026-51487","GHSA-c8xx-fr3x-6m5w"],"status":"published","title":"Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check","description":"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.","severity":{"version":"3.1","score":3.4,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00409,"percentile":0.35465,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1288"],"published":"2026-07-31T07:08:31Z","modified":"2026-09-17T14:45:11Z","fixes":[{"ecosystem":"Bitnami","package":"keycloak","fixed_in":["26.7.3"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Bitnami","package":"keycloak","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"26.7.3"}]}]}],"products":[{"vendor":"red hat","product":"red hat build of keycloak 26.6"},{"vendor":"red hat","product":"red hat build of keycloak 26.6.7"},{"vendor":"red hat","product":"red hat data grid 8"},{"vendor":"red hat","product":"red hat jboss enterprise application platform expansion pack"},{"vendor":"red hat","product":"red hat single sign-on 7"},{"vendor":"redhat","product":"build_of_keycloak"}],"references":[{"url":"https://access.redhat.com/errata/RHSA-2026:68277","tags":["vendor-advisory","x_refsource_REDHAT","web"]},{"url":"https://access.redhat.com/errata/RHSA-2026:68278","tags":["vendor-advisory","x_refsource_REDHAT","web"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-18209","tags":["vdb-entry","x_refsource_REDHAT","Vendor Advisory","advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2508305","tags":["issue-tracking","x_refsource_REDHAT","Issue Tracking","Vendor Advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-18209","tags":["web"]},{"url":"https://github.com/advisories/GHSA-c8xx-fr3x-6m5w"}],"sources":{"cve":[{"id":"CVE-2026-18209","title":"Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check","description":"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.","status":"published","published":"2026-07-31T07:08:31.373Z","modified":"2026-09-16T18:36:58.93Z","cvss":[{"version":"3.1","score":3.4,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-1288"],"updated_at":"2026-11-02T14:20:12.60856Z"}],"euvd":[{"id":"EUVD-2026-51487","description":"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.","status":"published","published":"2026-07-31T07:08:31Z","modified":"2026-09-16T18:36:58Z","cvss":[{"version":"3.1","score":3.4,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N","level":"low"}],"updated_at":"2026-11-02T17:28:14.33177Z"}],"ghsa":[{"id":"GHSA-c8xx-fr3x-6m5w","title":"A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect ...","description":"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.","status":"published","published":"2026-07-31T09:31:18Z","modified":"2026-09-16T18:32:20Z","cvss":[{"version":"3.1","score":3.4,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N","level":"low"}],"cwes":["CWE-1288"],"updated_at":"2026-11-02T15:12:01.408765Z"}],"nvd":[{"id":"CVE-2026-18209","description":"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.","status":"published","published":"2026-07-31T08:16:27.467Z","modified":"2026-09-16T19:17:08.72Z","cvss":[{"version":"3.1","score":3.4,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N","level":"low","assessor":"secondary"},{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-1288"],"updated_at":"2026-11-02T14:12:34.290716Z"}],"osv":[{"id":"BIT-keycloak-2026-18209","title":"Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check","description":"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.","status":"published","published":"2026-08-31T14:37:13.148Z","modified":"2026-09-17T14:45:11.101645029Z","updated_at":"2026-11-02T15:28:32.162822Z"}]}}