{"id":"CVE-2026-18209","title":"A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows","summary":"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 p…","severity":"low","cvss":3.4,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N","cwe":["CWE-1288"],"vendor":"redhat","product":"build_of_keycloak","affected":["build_of_keycloak"],"patched":["build_of_keycloak 26.6.7"],"published":"2026-07-31","updated":"2026-09-16","sourceUpdated":"2026-09-16T19:17:08.720","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-18209","references":[{"url":"https://access.redhat.com/errata/RHSA-2026:68277","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:68278","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/security/cve/CVE-2026-18209","label":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2508305","label":"secalert@redhat.com"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-18209.json"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-18209"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-18209"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00231,"epssPercentile":0.14216,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-07-31T15:56:41.018515Z"},"ingestedAt":"2026-08-08T14:22:57.429Z","slug":"CVE-2026-18209","body":"## Overview\n\nA 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.\n\n## Affected\n\n- `build_of_keycloak`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:68278** · Red Hat · fixed in: Red Hat build of Keycloak 26.6.7 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68278)\n- **RHSA-2026:68277** · Red Hat · fixed in: Red Hat build of Keycloak 26.6 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68277)","depth":"sunlit","depthScore":19,"depthScoreParts":{"impact":18.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}