Vulnerability Details CVE-2026-4634
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.005
EPSS Ranking 41.2%
CVSS Severity
CVSS v3 Score 7.5
References
- https://access.redhat.com/errata/RHSA-2026:6475
- https://access.redhat.com/errata/RHSA-2026:6476
- https://access.redhat.com/errata/RHSA-2026:6477
- https://access.redhat.com/errata/RHSA-2026:6478
- https://access.redhat.com/security/cve/CVE-2026-4634
- https://bugzilla.redhat.com/show_bug.cgi?id=2450250
- https://access.redhat.com/errata/RHSA-2026:6475
- https://access.redhat.com/errata/RHSA-2026:6476
- https://access.redhat.com/errata/RHSA-2026:6477
- https://access.redhat.com/errata/RHSA-2026:6478
- https://access.redhat.com/security/cve/CVE-2026-4634
- https://bugzilla.redhat.com/show_bug.cgi?id=2450250
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4634.json
Products affected by CVE-2026-4634
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cpe:2.3:a:redhat:build_of_keycloak:-
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cpe:2.3:a:redhat:build_of_keycloak:26.2
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cpe:2.3:a:redhat:build_of_keycloak:26.2.15
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cpe:2.3:a:redhat:build_of_keycloak:26.4
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cpe:2.3:a:redhat:build_of_keycloak:26.4.11