What is CVE-2026-2603?

CVE-2026-2603 is a high-severity vulnerability in Red Hat Build Of Keycloak 26.2, classified under Missing Authentication for Critical Function. CVSS score: 8.1/10. Published 2026-03-18.

How severe is CVE-2026-2603?

High severity. CVSS v3 base score is 8.1 out of 10.

Auth bypass in Red Hat Build Of Keycloak 26.2

CVE-2026-2603

A flaw was found in Keycloak. A remote attacker could bypass security controls by sending a valid SAML response from an external Identity Provider (IdP) to the Keycloak SAML endpoint for IdP-initiated broker logins. This allows the attacker to complete broker logins even when the SAML Identity Provider is disabled, leading to unauthorized authentication.

Vulnerability class: Broken Authentication

Published 2026-03-18 · last modified 2026-08-18.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.007 (52.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 52.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.003

Affected products

Red Hat Build Of Keycloak 26.2 — versions 26.2.14-1, 26.2-16
Red Hat Build Of Keycloak 26.2.14
Red Hat Build Of Keycloak 26.4 — versions 26.4.10-1, 26.4-12
Red Hat Build Of Keycloak 26.4.10
Red Hat Build Of Keycloak

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

References

access.redhat.com/errata/RHSA-2026:3925 (vendor-advisory, Vendor Advisory)
access.redhat.com/errata/RHSA-2026:3926 (vendor-advisory, Vendor Advisory)
access.redhat.com/errata/RHSA-2026:3947 (vendor-advisory, Vendor Advisory)
access.redhat.com/errata/RHSA-2026:3948 (vendor-advisory, Vendor Advisory)
access.redhat.com/security/cve/CVE-2026-2603 (vdb-entry, Vendor Advisory)
bugzilla.redhat.com/show_bug.cgi (issue-tracking, Exploit, Issue Tracking, Vendor Advisory)
0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Vendor Advisory)

Frequently asked questions

What is CVE-2026-2603?: CVE-2026-2603 is a high-severity vulnerability in Red Hat Build Of Keycloak 26.2, classified under Missing Authentication for Critical Function. CVSS score: 8.1/10. Published 2026-03-18.
How severe is CVE-2026-2603?: High severity. CVSS v3 base score is 8.1 out of 10.