Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login_CVE-2026-9087

{
    "lastseen": "",
    "description": "A flaw was found in Keycloak. The cross-session verification proof is keyed only by (local userId,\nidpAlias) and is not bound to the upstream identity that was actually verified, so a second upstream account on the same IdP can consume it and get linked to the victim's local account.",
    "published": "2026-05-20T16:13:03.022Z",
    "modified": "2026-05-20T16:13:03.022Z",
    "type": "cve",
    "title": "Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login",
    "source": "redhat",
    "references": "https://access.redhat.com/security/cve/CVE-2026-9087\nhttps://bugzilla.redhat.com/show_bug.cgi?id=2480172",
    "id": "CVE-2026-9087",
    "bulletinFamily": "",
    "cwe": [
        "CWE-639"
    ],
    "cvelist": null,
    "sourceData": "",
    "sourceHref": "",
    "cvss": {
        "score": 6.4,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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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
}