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Fencer Intel
high 7.5

CVE-2026-4634 json

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

published 7mo ago modified 14d ago also BIT-keycloak-2026-4634 , EUVD-2026-18212 , GHSA-h4wv-g838-66g3

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

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.

Patch / fix

  • maven org.keycloak:keycloak-services 26.5.7
  • bitnami keycloak 26.2.1, 26.3.0, 26.4.1, 26.5.0
  • Red Hat Red Hat build of Keycloak 26.2 26.2-18, 26.2.15-1
  • Red Hat Red Hat build of Keycloak 26.4 26.4-14, 26.4.11-1
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 7 0:18.0.20-1.redhat_00001.1.el7sso
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 8 0:18.0.20-1.redhat_00001.1.el8sso
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 9 0:18.0.20-1.redhat_00001.1.el9sso
  • Red Hat RHEL-8 based Middleware Containers 7.6-85
  • rh-sso7-keycloak red hat single sign on 7.6 18.0.20-1.redhat_00001.1.el8sso
  • rh-sso7-keycloak-server red hat single sign on 7.6 18.0.20-1.redhat_00001.1.el8sso
  • rh-sso7-keycloak red hat single sign on 7.6 18.0.20-1.redhat_00001.1.el9sso
  • rh-sso7-keycloak-server red hat single sign on 7.6 18.0.20-1.redhat_00001.1.el9sso
  • rh-sso7-keycloak red hat single sign on 7.6 18.0.20-1.redhat_00001.1.el7sso
  • rh-sso7-keycloak-server red hat single sign on 7.6 18.0.20-1.redhat_00001.1.el7sso

red hat advisories RHSA-2026:76129RHSA-2026:76130RHSA-2026:76128

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-4634 updated cvss 7.5

keycloak: Keycloak: Denial of Service via excessive processing of OpenID Connect scope parameters

  • Red Hat Middleware Containers for OpenShift rh-sso-7/sso76-openshift-rhel8 7.6-85
    fixed: vendor fix RHSA-2026:76134
  • Red Hat build of Keycloak 26.2 rhbk/keycloak-rhel9 26.2-18, rhbk/keycloak-rhel9-operator 26.2-18, rhbk/keycloak-operator-bundle 26.2.15-1
    fixed: vendor fix RHSA-2026:6476
  • Red Hat build of Keycloak 26.2.15
    fixed: vendor fix RHSA-2026:6475
  • Red Hat build of Keycloak 26.4 rhbk/keycloak-rhel9 26.4-14, rhbk/keycloak-rhel9-operator 26.4-14, rhbk/keycloak-operator-bundle 26.4.11-1
    fixed: vendor fix RHSA-2026:6478
  • Red Hat build of Keycloak 26.4.11
    fixed: vendor fix RHSA-2026:6477
  • 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
    fixed: vendor fix RHSA-2026:76128
  • 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
    fixed: vendor fix RHSA-2026:76129
  • 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
    fixed: vendor fix RHSA-2026:76130
show 1 more

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7mo ago

Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven org.keycloak:keycloak-services
<26.5.7
26.5.7
bitnami keycloak
>=26.2.0, <26.2.1
>=26.2.15, <26.3.0
>=26.4.0, <26.4.1
>=26.4.11, <26.5.0
26.2.1
26.3.0
26.4.1
26.5.0

Affected products

  • Red Hat Red Hat build of Keycloak 26.2
  • Red Hat Red Hat build of Keycloak 26.2.15
  • Red Hat Red Hat build of Keycloak 26.4
  • Red Hat Red Hat build of Keycloak 26.4.11
  • Red Hat Red Hat Single Sign-On 7.6.13
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 7
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 8
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 9
  • Red Hat RHEL-8 based Middleware Containers

Classification

Weakness
  • CWE-1050 Excessive Platform Resource Consumption within a Loop

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.