CVE-2026-9803

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

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

EPSS

0.4% chance of exploitation in the next 30 days; higher than 35% of CVEs (scores of 2026-10-25)

CWE

CWE-125

Published

2026-05-28

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

Affected

• redhat:build_of_keycloak

Packages (OSV)

References

• https://access.redhat.com/errata/RHSA-2026:25097
• https://access.redhat.com/errata/RHSA-2026:25098
• https://access.redhat.com/errata/RHSA-2026:30049
• https://access.redhat.com/errata/RHSA-2026:30050
• https://access.redhat.com/security/cve/CVE-2026-9803

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