CVE-2026-9803CWE-125

Keycloak: keycloak: denial of service via malformed authorization header

Medium · published May 28, 2026

CVSS v3.1
5.3
EPSS
1%
Percentile
53.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS v4.0
Not supplied
EPSS
0.00718 · 53.3th percentile
Weakness
CWE-125 · Out-of-bounds Read
Published
2026-05-28T04:47Z
EPSS history
Timeline
  • 28 MAY 04:47Z
    Keycloak: keycloak: denial of service via malformed authorization header
    cvelistv5