CVE-2026-4634
High
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.
SeverityHigh
CVSS7.5
Exploit probability—
Product
Redhat Build Of Keycloak
PublishedApr 2, 2026
First seenApr 2, 2026
Weakness typeCWE-1050CWE-1050
How to fix
Update
- org.keycloak:keycloak-services26.5.7 or later
Vendor advisories
- access.redhat.com/errata/RHSA-2026:6475
- access.redhat.com/errata/RHSA-2026:6476
- access.redhat.com/errata/RHSA-2026:6477
- access.redhat.com/errata/RHSA-2026:6478
- access.redhat.com/errata/RHSA-2026:76128
- access.redhat.com/errata/RHSA-2026:76129
- access.redhat.com/errata/RHSA-2026:76130
- access.redhat.com/errata/RHSA-2026:76132
- access.redhat.com/errata/RHSA-2026:76134
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| redhat build_of_keycloak | No range specified, 26.2, 26.2.15, 26.4, 26.4.11 | — |
| org.keycloak:keycloak-servicesMaven | v < 26.5.7 | 26.5.7 |
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