{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-9803", "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "state": "PUBLISHED", "assignerShortName": "redhat", "dateReserved": "2026-05-28T04:02:28.881Z", "datePublished": "2026-05-28T04:47:10.485Z", "dateUpdated": "2026-05-28T04:47:10.485Z"}, "containers": {"cna": {"title": "Keycloak: keycloak: denial of service via malformed authorization header", "metrics": [{"other": {"content": {"value": "Moderate", "namespace": "https://access.redhat.com/security/updates/classification/"}, "type": "Red Hat severity rating"}}, {"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "format": "CVSS"}], "descriptions": [{"lang": "en", "value": "A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service."}], "affected": [{"vendor": "Red Hat", "product": "Red Hat Build of Keycloak", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "rhbk/keycloak-rhel9", "defaultStatus": "affected", "cpes": ["cpe:/a:redhat:build_keycloak:"]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2026-9803", "tags": ["vdb-entry", "x_refsource_REDHAT"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2482465", "name": "RHBZ#2482465", "tags": ["issue-tracking", "x_refsource_REDHAT"]}], "datePublic": "2026-05-28T04:03:01.292Z", "problemTypes": [{"descriptions": [{"cweId": "CWE-125", "description": "Out-of-bounds Read", "lang": "en", "type": "CWE"}]}], "x_redhatCweChain": "CWE-125: Out-of-bounds Read", "workarounds": [{"lang": "en", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}], "timeline": [{"lang": "en", "time": "2026-05-28T04:02:15.892Z", "value": "Reported to Red Hat."}, {"lang": "en", "time": "2026-05-28T04:03:01.292Z", "value": "Made public."}], "credits": [{"lang": "en", "value": "Red Hat would like to thank Mustafa \u00c7etin for reporting this issue."}], "providerMetadata": {"orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "shortName": "redhat", "dateUpdated": "2026-05-28T04:47:10.485Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service."}], "id": "CVE-2026-9803", "lastModified": "2026-05-28T06:16:29.750", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "secalert@redhat.com", "type": "Primary"}]}, "published": "2026-05-28T06:16:29.750", "references": [{"source": "secalert@redhat.com", "url": "https://access.redhat.com/security/cve/CVE-2026-9803"}, {"source": "secalert@redhat.com", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2482465"}], "sourceIdentifier": "secalert@redhat.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-125"}], "source": "secalert@redhat.com", "type": "Primary"}]}

{"acknowledgement": "Red Hat would like to thank Mustafa \u00c7etin for reporting this issue.", "bugzilla": {"description": "keycloak: Keycloak: Denial of Service via malformed Authorization header", "id": "2482465", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2482465"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-125", "details": ["A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-9803", "package_state": [{"cpe": "cpe:/a:redhat:build_keycloak:", "fix_state": "Affected", "package_name": "rhbk/keycloak-rhel9", "product_name": "Red Hat Build of Keycloak"}], "public_date": "2026-05-28T04:03:01Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-9803\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-9803"], "statement": "A Moderate denial of service flaw was found in Keycloak's client registration endpoints. An unauthenticated attacker can send a specially crafted request with a malformed 'Authorization: Bearer' header, causing an ArrayIndexOutOfBoundsException and an HTTP 500 error. This can lead to a temporary disruption of service for the Keycloak instance.", "threat_severity": "Moderate"}