CVE-2026-9803
Keycloak: keycloak: denial of service via malformed authorization header
- State
- Published
- Severity
- 5.3 Medium
- Published
- May 28, 2026
- Updated
- Jun 26, 2026
- Reserved
- May 28, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | redhat |
Weaknesses
- CWE-125 Out-of-bounds Read
Affected Products
| Product | Versions |
|---|---|
Red Hat build of Keycloak 26.4Red Hat |
|
Red Hat build of Keycloak 26.4Red 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 26.6Red Hat |
|
Red Hat build of Keycloak 26.6Red Hat |
|
Red Hat build of Keycloak 26.6.3Red Hat |
References
- RHSA-2026:25097vendor-advisory
- RHSA-2026:25098vendor-advisory
- RHSA-2026:30049vendor-advisory
- RHSA-2026:30050vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-9803vdb-entry
- RHBZ#2482465issue-tracking
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