Nextcloud: Authentication Bypass in ID4me handling via Missing JWT Signature Verification in User OIDC_CVE-2026-45156

{
    "lastseen": "",
    "description": "Nextcloud is an open source content collaboration platform. From versions 0.3.0 to before 3.1.0, 5.0.0 to before 5.1.0, and 6.0.0 to before 6.4.0, a missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user. This issue has been patched in versions 3.1.0, 4.1.0, 5.1.0, 6.4.0 and 8.3.0.",
    "published": "2026-06-01T16:38:46.470Z",
    "modified": "2026-06-01T16:38:46.470Z",
    "type": "cve",
    "title": "Nextcloud: Authentication Bypass in ID4me handling via Missing JWT Signature Verification in User OIDC",
    "source": "GitHub_M",
    "references": "https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qqgv-fqwp-mjpp\nhttps://github.com/nextcloud/user_oidc/pull/1285\nhttps://hackerone.com/reports/3489490",
    "id": "CVE-2026-45156",
    "bulletinFamily": "",
    "cwe": [
        "CWE-287"
    ],
    "cvelist": null,
    "sourceData": "nextcloud security-advisories >= 0.3.0, < 3.1.0\nnextcloud security-advisories >= 5.0.0, < 5.1.0\nnextcloud security-advisories >= 6.0.0, < 6.4.0",
    "sourceHref": "",
    "cvss": {
        "score": 8.1,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "security-advisories",
    "version": ">= 0.3.0, < 3.1.0",
    "vendor": "nextcloud",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}