# CVE-2026-18208: Keycloak-services: keycloak-services: inactive out-of-audience token introspection leaks signed jwt claim

> An attacker can bypass audience restrictions to read sensitive token claims via the OIDC introspection endpoint in Keycloak.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 31 Jul 2026
- **Updated:** 31 Aug 2026
- **Also known as:** GHSA-jg59-c35g-76r8

## What is CVE-2026-18208?

CVE-2026-18208 is a medium-severity vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A flaw was found in the OIDC token introspection endpoint of the keycloak-services component. Keycloak is an open-source identity and access management solution used to secure modern applications and services. The issue occurs when a confidential client, configured to receive signed JWT introspection responses, attempts to introspect a token issued for a different audience. Although the endpoint correctly identifies the token as inactive for that client, it still returns the full set of token claims within a signed JWT field. This allows an unauthorized client to bypass audience-based restrictions and access sensitive information contained in the token.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-18208?

It affects 1 product.


Products: Redhat Build of Keycloak.

## How do I fix CVE-2026-18208?

No fix has been published for CVE-2026-18208 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-18208 being exploited?

There is no known exploitation of CVE-2026-18208 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Build of Keycloak

- [CVE-2026-15572](https://insights.sbomify.com/CVE-2026-15572/): Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation (high 8.8)
- [CVE-2026-3047](https://insights.sbomify.com/CVE-2026-3047/): Keycloak SAML Broken has Authentication Bypass by Primary Weakness (high 8.8)
- [CVE-2026-15573](https://insights.sbomify.com/CVE-2026-15573/): Keycloak-services: keycloak-services: authorization bypass via unnormalized uri matching in pathmatcher (high 8.1)
- [CVE-2026-16102](https://insights.sbomify.com/CVE-2026-16102/): Keycloak-services: keycloak-services: default dcr policy allows role forgery via user property mappers (high 8.1)
- [CVE-2026-1609](https://insights.sbomify.com/CVE-2026-1609/): Org.keycloak/keycloak-quarkus-server: keycloak: unauthorized access via jwt authorization grant with disabled users (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18208 and fix it if it is affected.

What it is: CVE-2026-18208 is a medium-severity vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-18208 in the wild and no public exploit code.

Affected product: Redhat Build of Keycloak. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-18208/ (Markdown: https://insights.sbomify.com/CVE-2026-18208/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18208
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18208
- OSV: https://osv.dev/vulnerability/CVE-2026-18208

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18208/
Summaries are generated and may contain mistakes; the official description above is the record.