CVE-2026-16442: Keycloak-services: keycloak-services: saml idp-initiated broker login bypasses link-only restriction

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-05 · updated 2026-08-10
Weakness: CWE-346

Description

A flaw was found in the SAML broker component of Keycloak, which is used to manage identity federation and user authentication. The issue occurs because the IdP-initiated Single Sign-On endpoint fails to check if a provider is restricted to account linking only. This allows an attacker with control over a linked upstream identity to bypass login restrictions and gain full access to a local user account.

Affected products

Red Hat build of Keycloak 26.4: from 26.4 before 26.4.14; from 26.6 before 26.6.5 — fixed in 26.4.14, 26.6.5

How to fix

Upgrade to a fixed version: Red Hat build of Keycloak 26.4 26.4.14, 26.6.5. Check the vendor advisory for mitigations.

References

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