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CVE-2023-6563

Keycloak: offline session token dos

7.7 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

1.24%Up 1.2 points since Dec 15, 2023
90%50%10%1%

What each source reports

CVE List Score used 7.7

Keycloak: offline session token dos

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.

Record
CVE-2023-6563
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-770
Updated
2026-11-02
EUVDEUVD-2023-3108 7.7

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.

Record
EUVD-2023-3108
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-54f3-c6hg-865h 7.7

Allocation of Resources Without Limits in Keycloak

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.

Record
GHSA-54f3-c6hg-865h
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-770
Updated
2026-11-02
NVD 7.7

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.

Record
CVE-2023-6563
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-770
Updated
2026-11-02
OSV 7.7

Keycloak: offline session token dos

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.

Record
CVE-2023-6563
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-770
Updated
2026-11-02
OSVGHSA-54f3-c6hg-865h 7.7

Allocation of Resources Without Limits in Keycloak

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.

Record
GHSA-54f3-c6hg-865h
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-770
Updated
2026-11-02
OSVRHSA-2023:7854 7.7

Red Hat Security Advisory: Red Hat Single Sign-On 7.6.6 security update on RHEL 7

Record
RHSA-2023:7854
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
OSVRHSA-2023:7855 7.7

Red Hat Security Advisory: Red Hat Single Sign-On 7.6.6 security update on RHEL 9

Record
RHSA-2023:7855
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
OSVRHSA-2023:7856 7.7

Red Hat Security Advisory: Red Hat Single Sign-On 7.6.6 security update on RHEL 8

Record
RHSA-2023:7856
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.keycloak:keycloak-model-jpa
Maven
 before 21.0.0
21.0.0
org.keycloak:keycloak-model-jpa
Maven
 before 21.0.0, plus listed versions
1.0-alpha-11.0-alpha-1-120620131.0-alpha-21.0-alpha-31.0-alpha-4
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1.0-beta-11.0-beta-1-201505211.0-beta-1-201505231.0-beta-21.0-beta-31.0-beta-41.0-final1.0-rc-11.0-rc-21.0.1.Final1.0.2.Final1.0.3.Final1.0.4.Final1.0.5.Final1.1.0.Beta11.1.0.Beta21.1.0.Final1.1.1.Final1.2.0.Beta11.2.0.CR11.2.0.Final1.3.0.Final1.3.1.Final1.4.0.Final1.5.0-Final1.5.0.Final1.5.1.Final1.6.0.Final1.6.1.Final1.7.0.CR11.7.0.Final1.8.0.Alpha11.8.0.CR11.8.0.CR21.8.0.CR31.8.0.Final1.8.1.Final1.9.0.CR11.9.0.Final1.9.1.Final1.9.2.Final1.9.3.Final1.9.4.Final1.9.5.Final1.9.7.Final
21.0.0
rh-sso7-keycloak
Red Hat:red_hat_single_sign_on:7.6::el7
From an advisory covering 3 CVEs
 before 0:18.0.11-2.redhat_00003.1.el7sso
0:18.0.11-2.redhat_00003.1.el7sso
rh-sso7-keycloak-server
Red Hat:red_hat_single_sign_on:7.6::el7
From an advisory covering 3 CVEs
 before 0:18.0.11-2.redhat_00003.1.el7sso
0:18.0.11-2.redhat_00003.1.el7sso
rh-sso7-keycloak
Red Hat:red_hat_single_sign_on:7.6::el9
From an advisory covering 3 CVEs
 before 0:18.0.11-2.redhat_00003.1.el9sso
0:18.0.11-2.redhat_00003.1.el9sso
rh-sso7-keycloak-server
Red Hat:red_hat_single_sign_on:7.6::el9
From an advisory covering 3 CVEs
 before 0:18.0.11-2.redhat_00003.1.el9sso
0:18.0.11-2.redhat_00003.1.el9sso
rh-sso7-keycloak
Red Hat:red_hat_single_sign_on:7.6::el8
From an advisory covering 3 CVEs
 before 0:18.0.11-2.redhat_00003.1.el8sso
0:18.0.11-2.redhat_00003.1.el8sso
rh-sso7-keycloak-server
Red Hat:red_hat_single_sign_on:7.6::el8
From an advisory covering 3 CVEs
 before 0:18.0.11-2.redhat_00003.1.el8sso
0:18.0.11-2.redhat_00003.1.el8sso

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2023-6563 is a high vulnerability (CVSS 7.7) in Redhat Keycloak, published December 14, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.24%, the 69th percentile. Fixed in org.keycloak:keycloak-model-jpa 21.0.0.

References

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