Denial of Service Vulnerability in Keycloak's ClientRegistrationAuth Component
CVE-2026-9803

5.3MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Build Of Keycloak
Vendor
CVE Published:
28 May 2026

What is CVE-2026-9803?

A vulnerability exists in Keycloak's ClientRegistrationAuth component, where a remote unauthenticated attacker can exploit this flaw by sending a specially crafted POST request containing a malformed 'Authorization: Bearer' header to client registration endpoints. This exploitation can trigger an ArrayIndexOutOfBoundsException, leading to an HTTP 500 error response from the server. Consequently, this results in a Denial of Service condition for the affected service, disrupting its availability.

References

https://access.redhat.com/security/cve/CVE-2026-9803
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2482465
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Red Hat would like to thank Mustafa Çetin for reporting this issue.
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