CVE-2026-9803

MEDIUM

Keycloak: keycloak: denial of service via malformed authorization header

Title source: cna
STIX 2.1

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.

References (4)

Core 4
Core References
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:25097
https://access.redhat.com/errata/RHSA-2026:25097
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:25098
https://access.redhat.com/errata/RHSA-2026:25098
Vdb Entry, X_Refsource_Redhat vdb-entry x_refsource_redhat
https://access.redhat.com/security/cve/CVE-2026-9803
Issue Tracking, X_Refsource_Redhat issue-tracking x_refsource_redhat
RHBZ#2482465
https://bugzilla.redhat.com/show_bug.cgi?id=2482465

Scores

CVSS v3 5.3
EPSS 0.0039
EPSS Percentile 30.5%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-125
Status published
Products (5)
Red Hat/Red Hat Build of Keycloak
Red Hat/Red Hat build of Keycloak 26.6 26.6-6
Red Hat/Red Hat build of Keycloak 26.6 26.6.3-3
Red Hat/Red Hat build of Keycloak 26.6.3
redhat/build_of_keycloak
Published May 28, 2026
Tracked Since May 28, 2026