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Build Of KeycloakApplication · Redhat

CVE-2026-4634

HIGH · 7.5 CVSS v3.1 Published 2026-04-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Keycloak contains a Denial of Service vulnerability in the OpenID Connect (OIDC) token endpoint. An unauthenticated attacker can send a POST request with an excessively long scope parameter, causing high resource consumption and prolonged processing times that render the server unavailable.

MitigationImplement input validation and length limits on the scope parameter at the OIDC token endpoint, and apply rate limiting to mitigate abuse.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Build Of KeycloakApplication
Affected:all versions= 26.2= 26.2.15= 26.4= 26.4.11

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm the deployed product is Red Hat Build of Keycloak
    Check the product name in the installation manifest, startup logs, or by querying the server's /health/ready endpoint. Upstream Keycloak is not affected; only the Red Hat Build variant falls under this CVE.
    Affected if The deployment is NOT the Red Hat Build of Keycloak - this CVE only applies to the Red Hat Build.
  2. Identify the installed version of Red Hat Build of Keycloak
    Check the installed RPM package version (rpm -q rhbk) or the version reported in the Keycloak server startup logs. Compare against affected versions: all versions, and specifically 26.2, 26.2.15, 26.4, 26.4.11.
    Affected if The installed version is any version of Red Hat Build of Keycloak.
  3. Verify the OIDC token endpoint is accessible
    Confirm the OIDC token endpoint is exposed (typically at /realms/{realm}/protocol/openid-connect/token). This endpoint handles POST requests with scope parameters.
    Affected if The OIDC token endpoint is not exposed or blocked from external access.
  4. Review server logs for scope parameter anomalies
    Examine Keycloak server logs for patterns of requests with unusually long scope parameter values or prolonged token endpoint processing times indicating resource exhaustion.
    Affected if No anomalous scope parameter patterns are found in logs and processing times are normal.
  5. Check for elevated resource consumption on token requests
    Monitor server CPU and memory usage during POST requests to the token endpoint, particularly with large scope values. Look for sustained high resource usage correlated with token requests.
    Affected if Resource usage remains normal and proportional to legitimate request volumes.

You are affected if you are running any version of Red Hat Build of Keycloak with the OIDC token endpoint exposed, as the vulnerability allows unauthenticated attackers to trigger excessive resource consumption via long scope parameters.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement input validation and length limits on the scope parameter at the OIDC token endpoint, and apply rate limiting to mitigate abuse.

Fix this in Build Of Keycloak Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-4634 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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