Vulnerability in Red Hat Build Of Keycloak 26.2
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.009 (57.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 57.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.009 · change: +0.003
Affected products
- Red Hat Build Of Keycloak 26.2 — versions 26.2.15-1, 26.2-18
- Red Hat Build Of Keycloak 26.2.15
- Red Hat Build Of Keycloak 26.4 — versions 26.4.11-1, 26.4-14
- Red Hat Build Of Keycloak 26.4.11
- Red Hat Single Sign-On 7
- Red Hat Build Of Keycloak — versions 26.2, 26.2.15, 26.4
Weakness classification (CWE)
References
- access.redhat.com/errata/RHSA-2026:6475 (vendor-advisory, Vendor Advisory)
- access.redhat.com/errata/RHSA-2026:6476 (vendor-advisory, Vendor Advisory)
- access.redhat.com/errata/RHSA-2026:6477 (vendor-advisory, Vendor Advisory)
- access.redhat.com/errata/RHSA-2026:6478 (vendor-advisory, Vendor Advisory)
- access.redhat.com/security/cve/CVE-2026-4634 (vdb-entry, Vendor Advisory)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Issue Tracking, Vendor Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- access.redhat.com/errata/RHSA-2026:76132 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:76134 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:76129 (vendor-advisory)
Frequently asked questions
- What is CVE-2026-4634?
- CVE-2026-4634 is a high-severity vulnerability in Red Hat Build Of Keycloak 26.2, classified under CWE-1050. CVSS score: 7.5/10. Published 2026-04-02.
- How severe is CVE-2026-4634?
- High severity. CVSS v3 base score is 7.5 out of 10.