What is CVE-2026-9803?

CVE-2026-9803 is a medium-severity vulnerability in Red Hat Build Of Keycloak, classified under Out-of-bounds Read. CVSS score: 5.3/10. Published 2026-05-28.

How severe is CVE-2026-9803?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Out-of-bounds Read in Red Hat Build Of Keycloak

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 reg…

Vulnerability class: Buffer Overflow

EPSS: 0.001 (26.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

Affected products

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

References

secalert@redhat.com (x_refsource_REDHAT, vdb-entry, Vendor Advisory)
secalert@redhat.com (x_refsource_REDHAT, issue-tracking, Issue Tracking, Vendor Advisory)

Frequently asked questions

What is CVE-2026-9803?: CVE-2026-9803 is a medium-severity vulnerability in Red Hat Build Of Keycloak, classified under Out-of-bounds Read. CVSS score: 5.3/10. Published 2026-05-28.
How severe is CVE-2026-9803?: Medium severity. CVSS v3 base score is 5.3 out of 10.