High

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

Type: advisorySource: Official CVE List1 source record

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.

Announced 2 Apr 2026Source revision 1

Original source ↗

CVE-2026-4634

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-4634

Red Hat build of Keycloak 26.2

Source reference: /containers/cna/affected/0/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.2

Source reference: /containers/cna/affected/1/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.2

Source reference: /containers/cna/affected/2/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.2.15

Source reference: /containers/cna/affected/3/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.4

Source reference: /containers/cna/affected/4/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.4

Source reference: /containers/cna/affected/5/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.4

Source reference: /containers/cna/affected/6/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat build of Keycloak 26.4.11

Source reference: /containers/cna/affected/7/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat Single Sign-On 7.6.13

Source reference: /containers/cna/affected/8/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat Single Sign-On 7.6 for RHEL 7

Source reference: /containers/cna/affected/9/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat Single Sign-On 7.6 for RHEL 8

Source reference: /containers/cna/affected/10/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Red Hat Single Sign-On 7.6 for RHEL 9

Source reference: /containers/cna/affected/11/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

RHEL-8 based Middleware Containers

Source reference: /containers/cna/affected/12/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.2::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.2",
    "versions": [
      {
        "status": "unaffected",
        "version": "26.2.15-1",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rhbk/keycloak-operator-bundle",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.2::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.2",
    "versions": [
      {
        "status": "unaffected",
        "version": "26.2-18",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rhbk/keycloak-rhel9",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.2::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.2",
    "versions": [
      {
        "status": "unaffected",
        "version": "26.2-18",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rhbk/keycloak-rhel9-operator",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.2::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.2.15",
    "packageName": "rhbk/keycloak-rhel9",
    "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
    "defaultStatus": "unaffected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.4::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.4",
    "versions": [
      {
        "status": "unaffected",
        "version": "26.4.11-1",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rhbk/keycloak-operator-bundle",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.4::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.4",
    "versions": [
      {
        "status": "unaffected",
        "version": "26.4-14",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rhbk/keycloak-rhel9",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.4::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.4",
    "versions": [
      {
        "status": "unaffected",
        "version": "26.4-14",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rhbk/keycloak-rhel9-operator",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:build_keycloak:26.4::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat build of Keycloak 26.4.11",
    "packageName": "rhbk/keycloak-rhel9",
    "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
    "defaultStatus": "unaffected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:red_hat_single_sign_on:7.6"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat Single Sign-On 7.6.13",
    "packageName": "keycloak-services",
    "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
    "defaultStatus": "unaffected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:red_hat_single_sign_on:7.6::el7"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat Single Sign-On 7.6 for RHEL 7",
    "versions": [
      {
        "status": "unaffected",
        "version": "0:18.0.20-1.redhat_00001.1.el7sso",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rh-sso7-keycloak",
    "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:red_hat_single_sign_on:7.6::el8"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat Single Sign-On 7.6 for RHEL 8",
    "versions": [
      {
        "status": "unaffected",
        "version": "0:18.0.20-1.redhat_00001.1.el8sso",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rh-sso7-keycloak",
    "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:red_hat_single_sign_on:7.6::el9"
    ],
    "vendor": "Red Hat",
    "product": "Red Hat Single Sign-On 7.6 for RHEL 9",
    "versions": [
      {
        "status": "unaffected",
        "version": "0:18.0.20-1.redhat_00001.1.el9sso",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rh-sso7-keycloak",
    "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
    "defaultStatus": "affected"
  },
  {
    "cpes": [
      "cpe:/a:redhat:rhosemc:1.0::el8"
    ],
    "vendor": "Red Hat",
    "product": "RHEL-8 based Middleware Containers",
    "versions": [
      {
        "status": "unaffected",
        "version": "7.6-85",
        "lessThan": "*",
        "versionType": "rpm"
      }
    ],
    "packageName": "rh-sso-7/sso76-openshift-rhel8",
    "collectionURL": "https://catalog.redhat.com/software/containers/",
    "defaultStatus": "affected"
  }
]

Related CVEs: CVE-2026-4634
Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event: #9417 · Revision 1
Added to Heist Feed: Sat, 24 Oct 2026 23:17:32 GMT
Publisher date: Thu, 02 Apr 2026 12:44:53 GMT

Read the original announcement