Keycloak: keycloak: denial of service via malformed authorization header
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 0.4%
exploitation probability
0.4%top 66% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Affected products
Red Hat · Red Hat build of Keycloak 26.4Red Hat · Red Hat build of Keycloak 26.4.13Red Hat · Red Hat build of Keycloak 26.6Red Hat · Red Hat build of Keycloak 26.6.3References
https://access.redhat.com/errata/RHSA-2026:25097https://access.redhat.com/errata/RHSA-2026:25098https://access.redhat.com/errata/RHSA-2026:30049https://access.redhat.com/errata/RHSA-2026:30050https://access.redhat.com/security/cve/CVE-2026-9803https://bugzilla.redhat.com/show_bug.cgi?id=2482465