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

> An attacker can cause a denial of service by triggering excessive memory consumption in Keycloak when loading offline sessions in the admin UI.

- **Severity:** High 7.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Dec 2023
- **Updated:** 22 Sep 2026
- **Also known as:** GHSA-54f3-c6hg-865h

## What is CVE-2023-6563?

CVE-2023-6563 is a high-severity denial of service vulnerability in Redhat Keycloak, published on 14 Dec 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2023-6563?

2 open source packages ship an affected version, including org.keycloak:keycloak-model-jpa. It affects 5 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.keycloak:keycloak-model-jpa` | Maven | All versions | 21.0.0 |
| `org.keycloak:keycloak-model-jpa` | Maven | All versions | 21.0.0 |

Products: Redhat Keycloak, Redhat Openshift Container Platform, Redhat Openshift Container Platform for Ibm Linuxone, Redhat Openshift Container Platform for Power, Redhat Single Sign-On.

## How do I fix CVE-2023-6563?

Upgrade org.keycloak:keycloak-model-jpa to 21.0.0 or later.

## Is CVE-2023-6563 being exploited?

There is no known exploitation of CVE-2023-6563 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Keycloak

- [CVE-2022-4361](https://insights.sbomify.com/CVE-2022-4361/): Keycloak vulnerable to cross-site scripting when validating URI-schemes on SAML and OIDC (critical 10.0)
- [CVE-2022-1245](https://insights.sbomify.com/CVE-2022-1245/): Keycloak vulnerable to privilege escalation on Token Exchange feature (critical 9.8)
- [CVE-2021-20195](https://insights.sbomify.com/CVE-2021-20195/): keycloak Self Stored Cross-site Scripting vulnerability (critical 9.6)
- [CVE-2019-14910](https://insights.sbomify.com/CVE-2019-14910/): Keycloak Authentication Error (critical 9.3)
- [CVE-2019-14909](https://insights.sbomify.com/CVE-2019-14909/): Keycloak Authentication Error (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6563 and fix it if it is affected.

What it is: CVE-2023-6563 is a high-severity denial of service vulnerability in Redhat Keycloak, published on 14 Dec 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-6563 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-model-jpa (Maven): affected all versions; fixed in 21.0.0
- org.keycloak:keycloak-model-jpa (Maven): affected all versions; fixed in 21.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-6563/ (Markdown: https://insights.sbomify.com/CVE-2023-6563/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6563
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6563
- OSV: https://osv.dev/vulnerability/CVE-2023-6563

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6563/
Summaries are generated and may contain mistakes; the official description above is the record.