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Fencer Vulns
high 7.7

CVE-2023-6563 json

Keycloak: offline session token dos

published 2023-12-14 2 y ago modified 2026-09-22 48 d ago also GHSA-54f3-c6hg-865h , EUVD-2023-3108

cvss
7.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 69%
public exploits
0
none known

Summary

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

Patch / fix

  • maven org.keycloak:keycloak-model-jpa 21.0.0
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 7 0:18.0.11-2.redhat_00003.1.el7sso
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 8 0:18.0.11-2.redhat_00003.1.el8sso
  • Red Hat Red Hat Single Sign-On 7.6 for RHEL 9 0:18.0.11-2.redhat_00003.1.el9sso
  • Red Hat RHEL-8 based Middleware Containers 7.6-38, 7.6.6-2
  • rh-sso7-keycloak red hat single sign on 7.6 18.0.11-2.redhat_00003.1.el9sso
  • rh-sso7-keycloak-server red hat single sign on 7.6 18.0.11-2.redhat_00003.1.el9sso
  • rh-sso7-keycloak red hat single sign on 7.6 18.0.11-2.redhat_00003.1.el8sso
  • rh-sso7-keycloak-server red hat single sign on 7.6 18.0.11-2.redhat_00003.1.el8sso
  • rh-sso7-keycloak red hat single sign on 7.6 18.0.11-2.redhat_00003.1.el7sso
  • rh-sso7-keycloak-server red hat single sign on 7.6 18.0.11-2.redhat_00003.1.el7sso

red hat advisories RHSA-2023:7855RHSA-2023:7856RHSA-2023:7854

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-2023-6563 updated cvss 7.7

keycloak: offline session token DoS

  • Red Hat Middleware Containers for OpenShift rh-sso-7/sso76-openshift-rhel8 7.6-38, rh-sso-7/sso7-rhel8-operator-bundle 7.6.6-2
    fixed: vendor fix RHSA-2023:7857
  • Red Hat Single Sign-On 7.6 for RHEL 7 Server rh-sso7-keycloak 18.0.11-2.redhat_00003.1.el7sso, rh-sso7-keycloak-server 18.0.11-2.redhat_00003.1.el7sso
    fixed: vendor fix RHSA-2023:7854
  • Red Hat Single Sign-On 7.6 for RHEL 8 rh-sso7-keycloak 18.0.11-2.redhat_00003.1.el8sso, rh-sso7-keycloak-server 18.0.11-2.redhat_00003.1.el8sso
    fixed: vendor fix RHSA-2023:7856
  • Red Hat Single Sign-On 7.6 for RHEL 9 rh-sso7-keycloak 18.0.11-2.redhat_00003.1.el9sso, rh-sso7-keycloak-server 18.0.11-2.redhat_00003.1.el9sso
    fixed: vendor fix RHSA-2023:7855
  • Red Hat Single Sign-On 7.6.6
    fixed: vendor fix RHSA-2023:7858
  • Red Hat Build of Keycloak keycloak-core
    not affected: vulnerable code not present

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

Exploit prediction

1.24% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • access.redhat.com https://access.redhat.com/errata/RHSA-2023:7857 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
NVD 3.1 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
GitHub 3.1 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven org.keycloak:keycloak-model-jpa
<21.0.0
21.0.0

Affected products

  • 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
  • Red Hat Single Sign-On 7.6.6
  • Red Hat Red Hat Build of Keycloak

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns 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.