Bug 2503138 (CVE-2026-16442)
| Summary: | CVE-2026-16442 keycloak-services: keycloak-services: SAML IdP-initiated broker login bypasses link-only restriction | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security DevOps Team <prodsec-dev> |
| Status: | NEW --- | QA Contact: | |
| Severity: | high | Docs Contact: | |
| Priority: | high | ||
| Version: | unspecified | CC: | anujha, aschwart, asoldano, aszczucz, bbaranow, bmaxwell, boliveir, bstansbe, dlofthou, drichtar, istudens, ivassile, iweiss, mosmerov, mposolda, msvehla, nwallace, pberan, pesilva, pjindal, pmackay, rmartinc, rstancel, security-response-team, ssilvert, sthorger, thjenkin, vdosoudi, vmuzikar |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | --- | |
| Doc Text: |
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.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Deadline: | 2026-10-15 | ||
A vulnerability was found in the keycloak-services component where the SAML IdP-initiated broker login endpoint fails to enforce the link-only identity provider restriction. When a SAML identity provider is configured with linkOnly=true, it is intended to only allow users to link their accounts, not to use that provider for logging in. However, the endpoint at /realms/{realm}/broker/{alias}/endpoint/clients/{client_id} does not validate this setting. An attacker who controls an upstream SAML identity already linked to a Keycloak user can submit a valid signed SAML response directly to this endpoint. This allows the attacker to bypass the restriction and obtain a full authenticated session as the linked local user.