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TI-2026-04036 Aliases CVE-2026-4634GHSA-h4wv-g838-66g3

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

Priority MEDIUM 40CWE-1050Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00638 50th percentileScored 2026-11-07
Fix Fixed org.keycloak:keycloak-services (Maven): 26.5.7Red Hat: 9 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Red HatRed Hat build of Keycloak 26.2—26.2.15-1Patch availableCNA
Red HatRed Hat build of Keycloak 26.2—26.2-18Patch availableCNA
Red HatRed Hat build of Keycloak 26.2—26.2-18Patch availableCNA
Red HatRed Hat build of Keycloak 26.2.15——Not affectedCNA
Red HatRed Hat build of Keycloak 26.4—26.4.11-1Patch availableCNA
Red HatRed Hat build of Keycloak 26.4—26.4-14Patch availableCNA
Red HatRed Hat build of Keycloak 26.4—26.4-14Patch availableCNA
Red HatRed Hat build of Keycloak 26.4.11——Not affectedCNA
Red HatRed Hat Single Sign-On 7.6.13——Not affectedCNA
Red HatRed Hat Single Sign-On 7.6 for RHEL 7—18.0.20-1.redhat_00001.1.el7ssoPatch availableCNA
Red HatRed Hat Single Sign-On 7.6 for RHEL 8—18.0.20-1.redhat_00001.1.el8ssoPatch availableCNA
Red HatRed Hat Single Sign-On 7.6 for RHEL 9—18.0.20-1.redhat_00001.1.el9ssoPatch availableCNA
Red HatRHEL-8 based Middleware Containers—7.6-85Patch availableCNA
—org.keycloak:keycloak-services (Maven)before 26.5.726.5.7Patch availableGHSA-h4wv-g838-66g3
  • Red Hat build of Keycloak 26.2 VendorRed Hat Affected — Fixed in 26.2.15-1 Patch available CNA
  • Red Hat build of Keycloak 26.2 VendorRed Hat Affected — Fixed in 26.2-18 Patch available CNA
  • Red Hat build of Keycloak 26.2 VendorRed Hat Affected — Fixed in 26.2-18 Patch available CNA
  • Red Hat build of Keycloak 26.2.15 VendorRed Hat Affected — Fixed in — Not affected CNA
  • Red Hat build of Keycloak 26.4 VendorRed Hat Affected — Fixed in 26.4.11-1 Patch available CNA
  • Red Hat build of Keycloak 26.4 VendorRed Hat Affected — Fixed in 26.4-14 Patch available CNA
  • Red Hat build of Keycloak 26.4 VendorRed Hat Affected — Fixed in 26.4-14 Patch available CNA
  • Red Hat build of Keycloak 26.4.11 VendorRed Hat Affected — Fixed in — Not affected CNA
  • Red Hat Single Sign-On 7.6.13 VendorRed Hat Affected — Fixed in — Not affected CNA
  • Red Hat Single Sign-On 7.6 for RHEL 7 VendorRed Hat Affected — Fixed in 18.0.20-1.redhat_00001.1.el7sso Patch available CNA
  • Red Hat Single Sign-On 7.6 for RHEL 8 VendorRed Hat Affected — Fixed in 18.0.20-1.redhat_00001.1.el8sso Patch available CNA
  • Red Hat Single Sign-On 7.6 for RHEL 9 VendorRed Hat Affected — Fixed in 18.0.20-1.redhat_00001.1.el9sso Patch available CNA
  • RHEL-8 based Middleware Containers VendorRed Hat Affected — Fixed in 7.6-85 Patch available CNA
  • org.keycloak:keycloak-services (Maven) Vendor— Affected before 26.5.7 Fixed in 26.5.7 Patch available GHSA-h4wv-g838-66g3

CPE configurations NVD · 5

CPEVersionsRoleVendor
cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:text-only:*:*:*not specified by NVDVulnerableRed Hat
cpe:2.3:a:redhat:build_of_keycloak:26.2:*:*:*:text-only:*:*:*26.2VulnerableRed Hat
cpe:2.3:a:redhat:build_of_keycloak:26.2.15:*:*:*:text-only:*:*:*26.2.15VulnerableRed Hat
cpe:2.3:a:redhat:build_of_keycloak:26.4:*:*:*:text-only:*:*:*26.4VulnerableRed Hat
cpe:2.3:a:redhat:build_of_keycloak:26.4.11:*:*:*:text-only:*:*:*26.4.11VulnerableRed Hat
  • cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:text-only:*:*:* Versions not specified by NVD Vulnerable ·Red Hat
  • cpe:2.3:a:redhat:build_of_keycloak:26.2:*:*:*:text-only:*:*:* Versions 26.2 Vulnerable ·Red Hat
  • cpe:2.3:a:redhat:build_of_keycloak:26.2.15:*:*:*:text-only:*:*:* Versions 26.2.15 Vulnerable ·Red Hat
  • cpe:2.3:a:redhat:build_of_keycloak:26.4:*:*:*:text-only:*:*:* Versions 26.4 Vulnerable ·Red Hat
  • cpe:2.3:a:redhat:build_of_keycloak:26.4.11:*:*:*:text-only:*:*:* Versions 26.4.11 Vulnerable ·Red Hat

Remediation

  • Fix · GHSA-h4wv-g838-66g3 org.keycloak:keycloak-services (Maven) Fixed in 26.5.7 Advisory →

Red Hat 9 advisories

  • RHSA-2026:76128 Released 2026-10-06 · Red Hat rating Important
    Red Hat Single Sign-On 7.6.13 security update on RHEL 7
    • Red Hat Single Sign-On 7.6 for RHEL 7 Server rh-sso7-keycloak-18.0.20-1.redhat_00001.1.el7sso, rh-sso7-keycloak-server-18.0.20-1.redhat_00001.1.el7sso
  • RHSA-2026:76130 Released 2026-10-06 · Red Hat rating Important
    Red Hat Single Sign-On 7.6.13 security update on RHEL 9
    • Red Hat Single Sign-On 7.6 for RHEL 9 rh-sso7-keycloak-18.0.20-1.redhat_00001.1.el9sso, rh-sso7-keycloak-server-18.0.20-1.redhat_00001.1.el9sso
  • RHSA-2026:76129 Released 2026-10-06 · Red Hat rating Important
    Red Hat Single Sign-On 7.6.13 security update on RHEL 8
    • Red Hat Single Sign-On 7.6 for RHEL 8 rh-sso7-keycloak-18.0.20-1.redhat_00001.1.el8sso, rh-sso7-keycloak-server-18.0.20-1.redhat_00001.1.el8sso
Show 6 more Red Hat advisories
  • RHSA-2026:76134 Released 2026-10-05 · Red Hat rating Important
    Red Hat Single Sign-On 7.6.13 for OpenShift image security update
    • Middleware Containers for OpenShift rh-sso-7/sso76-openshift-rhel8
  • RHSA-2026:76132 Released 2026-10-05 · Red Hat rating Important
    Red Hat Single Sign-On 7.6.13 security update
    • Red Hat Single Sign-On 7.6.13
  • RHSA-2026:6478 Released 2026-04-02 · Red Hat rating Important
    Red Hat build of Keycloak 26.4.11 Images Update
    • Red Hat build of Keycloak 26.4 rhbk/keycloak-operator-bundle, rhbk/keycloak-rhel9, rhbk/keycloak-rhel9-operator
  • RHSA-2026:6476 Released 2026-04-02 · Red Hat rating Important
    Red Hat build of Keycloak 26.2.15 Images Update
    • Red Hat build of Keycloak 26.2 rhbk/keycloak-operator-bundle, rhbk/keycloak-rhel9, rhbk/keycloak-rhel9-operator
  • RHSA-2026:6477 Released 2026-04-02 · Red Hat rating Important
    Red Hat build of Keycloak 26.4.11 Update
    • Red Hat build of Keycloak 26.4.11
  • RHSA-2026:6475 Released 2026-04-02 · Red Hat rating Important
    Red Hat build of Keycloak 26.2.15 Update
    • Red Hat build of Keycloak 26.2.15

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Advisory ·

    Red Hat build of Keycloak 26.2, Red Hat build of Keycloak 26.2.15 and 2 more products — RHSA-2026:6475

    5 records Highest priority Priority MEDIUM 1 MEDIUM, 4 LOW

    Other records, highest priority first

    • TI-2026-04038 Keycloak: keycloak: uma policy bypass allows authenticated users to gain unauthorized access to victim-owned resources.Priority LOW 38
    • TI-2026-03727 Keycloak: keycloak: privilege escalation via forged authorization codes due to singleuseobjectprovider isolation flawPriority LOW 35
    • TI-2026-03352 Keycloak: keycloak: information disclosure due to redirect_uri validation bypassPriority LOW 34
    Show all 5 records → Advisory →
  • Advisory ·

    Red Hat build of Keycloak 26.2, Red Hat build of Keycloak 26.2.15 and 2 more products — RHSA-2026:6476

    5 records Highest priority Priority MEDIUM 1 MEDIUM, 4 LOW

    Other records, highest priority first

    • TI-2026-04038 Keycloak: keycloak: uma policy bypass allows authenticated users to gain unauthorized access to victim-owned resources.Priority LOW 38
    • TI-2026-03727 Keycloak: keycloak: privilege escalation via forged authorization codes due to singleuseobjectprovider isolation flawPriority LOW 35
    • TI-2026-03352 Keycloak: keycloak: information disclosure due to redirect_uri validation bypassPriority LOW 34
    Show all 5 records → Advisory →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Middleware Containers for OpenShiftFixed RHSA-2026:76134
Red Hat Single Sign-On 7.6 for RHEL 7 ServerFixed RHSA-2026:76128
Red Hat Single Sign-On 7.6 for RHEL 8Fixed RHSA-2026:76129
Red Hat Single Sign-On 7.6 for RHEL 9Fixed RHSA-2026:76130
Red Hat Single Sign-On 7.6.13Fixed RHSA-2026:76132
Red Hat build of Keycloak 26.2Fixed RHSA-2026:6476
Red Hat build of Keycloak 26.2.15Fixed RHSA-2026:6475
Red Hat build of Keycloak 26.4Fixed RHSA-2026:6478
Red Hat build of Keycloak 26.4.11Fixed RHSA-2026:6477

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-4634
  2. 2026-10-03 Alias added: GHSA-h4wv-g838-66g3
  3. 2026-10-06 Fix available: rh-sso-7/[email protected] · CNA
  4. 2026-10-06 2 new references · CNA
  5. 2026-10-06 Fix available: RHSA-2026:76134 · Red Hat
  6. 2026-10-06 Fix available: RHSA-2026:76132 · Red Hat
  7. 2026-10-06 Fix available: RHSA-2026:76129 · Red Hat
  8. 2026-10-06 Fix available: RHSA-2026:76130 · Red Hat
  9. 2026-10-06 Fix available: Middleware Containers for OpenShift, Red Hat Single Sign-On 7.6 for RHEL 8, Red Hat Single Sign-On 7.6 for RHEL 9 +1 · Red Hat
  10. 2026-10-06 Fix available: rh-sso7-keycloak@0:18.0.20-1.redhat_00001.1.el8sso, rh-sso7-keycloak@0:18.0.20-1.redhat_00001.1.el9sso · CNA
  11. 2026-10-06 2 new references · CNA
  12. 2026-10-06 Fix available: rh-sso7-keycloak@0:18.0.20-1.redhat_00001.1.el7sso · CNA
  13. 2026-10-06 1 new reference · CNA
  14. 2026-10-07 Fix available: RHSA-2026:76128 · Red Hat
  15. 2026-10-07 Fix available: Red Hat Single Sign-On 7.6 for RHEL 7 Server · Red Hat
  16. 2026-10-25 EPSS moved to the below the 50th percentile
  17. 2026-10-30 EPSS moved to the 50th–90th percentile

References

Advisory 12

Other 3

  • TI-2026-02223 Keycloak: keycloak: unauthorized authentication via disabled saml identity provider CVSS 3.1HIGH 8.1
  • TI-2024-01049 Keycloak: path transversal in redirection validation CVSS 3.1HIGH 8.1
  • TI-2026-13740 Keycloak-services: keycloak-services: saml idp-initiated broker login bypasses link-only restriction CVSS 3.1CRITICAL 9.8
  • TI-2026-13741 Keycloak-services: keycloak-services: saml broker metadata import disables response signature validation CVSS 3.1CRITICAL 9.1
  • TI-2026-13106 Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation CVSS 3.1HIGH 8.8
  • TI-2026-02631 Authentication bypass in Red Hat build of Keycloak 26.2 CVSS 3.1HIGH 8.8
See all 110 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences