Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.5%
exploitation probability
0.5%top 57% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
Red Hat · Red Hat build of Keycloak 26.2Red Hat · Red Hat build of Keycloak 26.2.15Red Hat · Red Hat build of Keycloak 26.4Red Hat · Red Hat build of Keycloak 26.4.11References
https://access.redhat.com/errata/RHSA-2026:6475https://access.redhat.com/errata/RHSA-2026:6476https://access.redhat.com/errata/RHSA-2026:6477https://access.redhat.com/errata/RHSA-2026:6478https://access.redhat.com/security/cve/CVE-2026-4634https://bugzilla.redhat.com/show_bug.cgi?id=2450250https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4634.json