CVE-2026-9803 — Keycloak: keycloak: denial of service via malformed authorization header
A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request wit…
Published: 2026-05-28 · CVSS: 5.3 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7