Keycloak: org.keycloak.protocol.oidc.grants.ciba: keycloak: information disclosure via cors header injection due to unvalidated jwt azp claim_CVE-2026-37977

{
    "lastseen": "",
    "description": "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: [\"*\"]`.",
    "published": "2026-04-06T08:38:36.657Z",
    "modified": "2026-04-06T11:57:17.383Z",
    "type": "cve",
    "title": "Keycloak: org.keycloak.protocol.oidc.grants.ciba: keycloak: information disclosure via cors header injection due to unvalidated jwt azp claim",
    "source": "redhat",
    "references": "https://access.redhat.com/security/cve/CVE-2026-37977\nhttps://bugzilla.redhat.com/show_bug.cgi?id=2455324",
    "id": "CVE-2026-37977",
    "bulletinFamily": "",
    "cwe": [
        "CWE-346"
    ],
    "cvelist": null,
    "sourceData": "",
    "sourceHref": "",
    "cvss": {
        "score": 3.7,
        "severity": "LOW",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
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        "privilegesRequired": "",
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        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Red Hat Build of Keycloak",
    "version": "",
    "vendor": "Red Hat",
    "ai_description": "",
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    "ai_score": 0
}