{"id":"CVE-2026-4634","title":"A flaw was found in Keycloak","summary":"A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-1050"],"vendor":"redhat","product":"build_of_keycloak","affected":["build_of_keycloak","build_of_keycloak = 26.2","build_of_keycloak = 26.2.15","build_of_keycloak = 26.4","build_of_keycloak = 26.4.11"],"patched":["middleware_containers_for_openshift","build_of_keycloak 26.2","build_of_keycloak 26.4","single_sign_on 7.6.13","build_of_keycloak 26.2.15","build_of_keycloak 26.4.11"],"published":"2026-04-02","updated":"2026-10-06","sourceUpdated":"2026-10-06T17:17:26.293","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-4634","references":[{"url":"https://access.redhat.com/errata/RHSA-2026:6475","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:6476","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:6477","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:6478","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:76128","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:76129","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:76130","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:76132","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:76134","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/security/cve/CVE-2026-4634","label":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2450250","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:6475","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:6476","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:6477","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:6478","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/security/cve/CVE-2026-4634","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2450250","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4634.json","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-4634"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-4634"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-04-03T17:22:51.847497Z"},"epss":0.00627,"epssPercentile":0.49827,"ingestedAt":"2026-09-29T16:39:33.224Z","slug":"CVE-2026-4634","body":"## Overview\n\nA flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.\n\n## Affected\n\n- `build_of_keycloak`\n- `build_of_keycloak = 26.2`\n- `build_of_keycloak = 26.2.15`\n- `build_of_keycloak = 26.4`\n- `build_of_keycloak = 26.4.11`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:76134** · Red Hat · fixed in: Middleware Containers for OpenShift · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:76134)\n- **RHSA-2026:6476** · Red Hat · fixed in: Red Hat build of Keycloak 26.2 · released 2026-04-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:6476)\n- **RHSA-2026:6478** · Red Hat · fixed in: Red Hat build of Keycloak 26.4 · released 2026-04-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:6478)\n- **RHSA-2026:76132** · Red Hat · fixed in: Red Hat Single Sign-On 7.6.13 · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:76132)\n- **RHSA-2026:6475** · Red Hat · fixed in: Red Hat build of Keycloak 26.2.15 · released 2026-04-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:6475)\n- **RHSA-2026:6477** · Red Hat · fixed in: Red Hat build of Keycloak 26.4.11 · released 2026-04-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:6477)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}