{
  "threat_severity" : "Low",
  "public_date" : "2026-04-06T08:34:01Z",
  "bugzilla" : {
    "description" : "keycloak: org.keycloak.protocol.oidc.grants.ciba: Keycloak: Information disclosure via CORS header injection due to unvalidated JWT azp claim",
    "id" : "2455324",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2455324"
  },
  "cvss3" : {
    "cvss3_base_score" : "3.7",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
    "status" : "verified"
  },
  "cwe" : "CWE-346",
  "details" : [ "A flaw was found in Keycloak. A remote attacker can exploit a Cross-Origin Resource Sharing (CORS) header injection vulnerability in Keycloak's User-Managed Access (UMA) token endpoint. This flaw occurs because the `azp` claim from a client-supplied JSON Web Token (JWT) is used to set the `Access-Control-Allow-Origin` header before the JWT signature is validated. When a specially crafted JWT with an attacker-controlled `azp` value is processed, this value is reflected as the CORS origin, even if the grant is later rejected. This can lead to the exposure of low-sensitivity information from authorization server error responses, weakening origin isolation, but only when a target client is misconfigured with `webOrigins: [\"*\"]`.", "A flaw was found in Keycloak. A remote attacker can exploit a Cross-Origin Resource Sharing (CORS) header injection vulnerability in Keycloak's User-Managed Access (UMA) token endpoint. This flaw occurs because the `azp` claim from a client-supplied JSON Web Token (JWT) is used to set the `Access-Control-Allow-Origin` header before the JWT signature is validated. When a specially crafted JWT with an attacker-controlled `azp` value is processed, this value is reflected as the CORS origin, even if the grant is later rejected. This can lead to the exposure of low-sensitivity information from authorization server error responses, weakening origin isolation, but only when a target client is misconfigured with `webOrigins: [\"*\"]`." ],
  "statement" : "Low impact: This vulnerability in Keycloak's UMA token endpoint allows for CORS header injection when a client is misconfigured with `webOrigins: [\"*\"]`. This can lead to the exposure of low-sensitivity information from authorization server error responses. Exploitation requires a specific client misconfiguration and does not affect default Keycloak installations.",
  "affected_release" : [ {
    "product_name" : "Red Hat build of Keycloak 26.4",
    "release_date" : "2026-06-25T00:00:00Z",
    "advisory" : "RHSA-2026:30050",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.4::el9",
    "package" : "rhbk/keycloak-operator-bundle:26.4.13-1"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.4",
    "release_date" : "2026-06-25T00:00:00Z",
    "advisory" : "RHSA-2026:30050",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.4::el9",
    "package" : "rhbk/keycloak-rhel9:26.4-19"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.4",
    "release_date" : "2026-06-25T00:00:00Z",
    "advisory" : "RHSA-2026:30050",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.4::el9",
    "package" : "rhbk/keycloak-rhel9-operator:26.4-19"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.4.13",
    "release_date" : "2026-06-25T00:00:00Z",
    "advisory" : "RHSA-2026:30049",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.4::el9",
    "package" : "rhbk/keycloak-rhel9"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.6",
    "release_date" : "2026-06-10T00:00:00Z",
    "advisory" : "RHSA-2026:25097",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.6::el9",
    "package" : "rhbk/keycloak-operator-bundle:26.6.3-3"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.6",
    "release_date" : "2026-06-10T00:00:00Z",
    "advisory" : "RHSA-2026:25097",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.6::el9",
    "package" : "rhbk/keycloak-rhel9:26.6-6"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.6",
    "release_date" : "2026-06-10T00:00:00Z",
    "advisory" : "RHSA-2026:25097",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.6::el9",
    "package" : "rhbk/keycloak-rhel9-operator:26.6-6"
  }, {
    "product_name" : "Red Hat build of Keycloak 26.6.3",
    "release_date" : "2026-06-10T00:00:00Z",
    "advisory" : "RHSA-2026:25098",
    "cpe" : "cpe:/a:redhat:build_keycloak:26.6::el9",
    "package" : "rhbk/keycloak-rhel9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-37977\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-37977" ],
  "name" : "CVE-2026-37977",
  "csaw" : false
}