CVE-2026-4634

HIGH

Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters

Title source: cna
STIX 2.1

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.

References (6)

Core 6
Core References
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:6475
https://access.redhat.com/errata/RHSA-2026:6475
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:6476
https://access.redhat.com/errata/RHSA-2026:6476
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:6477
https://access.redhat.com/errata/RHSA-2026:6477
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:6478
https://access.redhat.com/errata/RHSA-2026:6478
Vdb Entry, X_Refsource_Redhat vdb-entry x_refsource_redhat
https://access.redhat.com/security/cve/CVE-2026-4634
Issue Tracking, X_Refsource_Redhat issue-tracking x_refsource_redhat
RHBZ#2450250
https://bugzilla.redhat.com/show_bug.cgi?id=2450250

Scores

CVSS v3 7.5
EPSS 0.0002
EPSS Percentile 7.0%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-1050
Status published
Products (12)
org.keycloak/keycloak-services 0 - 26.5.7Maven
Red Hat/Red Hat build of Keycloak 26.2 26.2-18
Red Hat/Red Hat build of Keycloak 26.2 26.2.15-1
Red Hat/Red Hat build of Keycloak 26.2.15
Red Hat/Red Hat build of Keycloak 26.4 26.4-14
Red Hat/Red Hat build of Keycloak 26.4 26.4.11-1
Red Hat/Red Hat build of Keycloak 26.4.11
redhat/build_of_keycloak
redhat/build_of_keycloak 26.2
redhat/build_of_keycloak 26.2.15
... and 2 more
Published Apr 02, 2026
Tracked Since Apr 02, 2026