Description
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 resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.
Affected products
redhat: build of keycloak
References10
- access.redhat.com/errata/RHSA-2026:6475 Vendor Advisory
- access.redhat.com/errata/RHSA-2026:6476 Vendor Advisory
- access.redhat.com/errata/RHSA-2026:6477 Vendor Advisory
- access.redhat.com/errata/RHSA-2026:6478 Vendor Advisory
- access.redhat.com/security/cve/CVE-2026-4634 Vendor Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2450250 Issue TrackingVendor Advisory
- access.redhat.com/errata/RHSA-2026:6475 Vendor Advisory
- access.redhat.com/errata/RHSA-2026:6476 Vendor Advisory
- access.redhat.com/errata/RHSA-2026:6477 Vendor Advisory
- access.redhat.com/errata/RHSA-2026:6478 Vendor Advisory
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 1% percentile: 51 · as of 12 November 2026
- CWE
- CWE-1050
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