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Description

A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.

PUBLISHED Reserved 2026-05-28 | Published 2026-05-28 | Updated 2026-05-28 | Assigner redhat




MEDIUM: 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Problem types

Out-of-bounds Read

Product status

Default status
affected

Timeline

2026-05-28:Reported to Red Hat.
2026-05-28:Made public.

Credits

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

References

access.redhat.com/security/cve/CVE-2026-9803 vdb-entry

bugzilla.redhat.com/show_bug.cgi?id=2482465 (RHBZ#2482465) issue-tracking

cve.org (CVE-2026-9803)

nvd.nist.gov (CVE-2026-9803)

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