Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters
Summary
| CVE | CVE-2026-4634 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-04-02 13:16:27 UTC |
| Updated | 2026-07-15 02:22:43 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.005230000 probability, percentile 0.409030000 (date 2026-07-18)
Problem Types: CWE-1050 | CWE-1050 Excessive Platform Resource Consumption within a Loop
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | [email protected] | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Redhat | Build Of Keycloak | - | All | All | All |
| Application | Redhat | Build Of Keycloak | 26.2 | All | All | All |
| Application | Redhat | Build Of Keycloak | 26.2.15 | All | All | All |
| Application | Redhat | Build Of Keycloak | 26.4 | All | All | All |
| Application | Redhat | Build Of Keycloak | 26.4.11 | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Build Of Keycloak 26.2 | unaffected 26.2.15-1 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.2 | unaffected 26.2-18 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.2 | unaffected 26.2-18 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.2.15 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4.11-1 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4-14 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4-14 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4.11 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.2 | unaffected 26.2.15-1 * rpm | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.2 | unaffected 26.2-18 * rpm | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.2 | unaffected 26.2-18 * rpm | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.2.15 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4.11-1 * rpm | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4-14 * rpm | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4-14 * rpm | Not specified |
| ADP | Red Hat | Red Hat Build Of Keycloak 26.4.11 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/errata/RHSA-2026:6477 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:6475 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | Vendor Advisory |
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4634.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-4634 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:6478 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:6476 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | Vendor Advisory |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | Issue Tracking, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Evan Hendra (Independent Security Researcher) for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-03-23T08:40:02.817Z | Reported to Red Hat. |
| CNA | 2026-04-02T12:30:00.000Z | Made public. |
| ADP | 2026-03-23T08:40:02.817Z | Reported to Red Hat. |
| ADP | 2026-04-02T12:30:00.000Z | Made public. |
Solutions
ADP: RHSA-2026:6476: Red Hat build of Keycloak 26.2
ADP: RHSA-2026:6478: Red Hat build of Keycloak 26.4
ADP: RHSA-2026:6475: Red Hat build of Keycloak 26.2.15
ADP: RHSA-2026:6477: Red Hat build of Keycloak 26.4.11
Workarounds
CNA: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.