CVE-2026-9087

Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login

Published May 20, 2026 CVSS 3.1 · 6.4 Medium EPSS < 1% KEV · Not listed
Description
A flaw was found in Keycloak. The cross-session verification proof is keyed only by (local userId,
idpAlias) and is not bound to the upstream identity that was actually verified, so a second upstream account on the same IdP can consume it and get linked to the victim's local account.

Remediation

Vendor Workaround

To mitigate this issue, configure the affected identity provider to set `trustEmail=true`. This ensures that Keycloak trusts the email address provided by the upstream identity provider, bypassing the vulnerable verification flow. This mitigation should only be applied if the upstream identity provider is fully trusted to verify email addresses and prevent malicious account creation with existing email addresses. Configuration changes may require a Keycloak service restart or reload to take effect.

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-m6qj-3mpp-57v8 Keycloak: Insufficient verification proof scoping enables identity provider account linking attack and account compromise
History
Type Values Removed Values Added
CPEs cpe:/a:redhat:build_keycloak: cpe:/a:redhat:build_keycloak:26.6::el9
References
Type Values Removed Values Added
CPEs cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Redhat build Of Keycloak
Vendors & Products Redhat build Of Keycloak
Type Values Removed Values Added
Description A flaw was found in Keycloak. The cross-session verification proof is keyed only by (local userId, idpAlias) and is not bound to the upstream identity that was actually verified, so a second upstream account on the same IdP can consume it and get linked to the victim's local account.
Title Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login
First Time appeared Redhat
Redhat build Keycloak
Weaknesses CWE-639
CPEs cpe:/a:redhat:build_keycloak:
Vendors & Products Redhat
Redhat build Keycloak
References
Metrics cvssV3_1

{'score': 6.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Aug 3, 2026, 10:41 AM
Reserved
May 20, 2026, 2:53 PM
Status
Modified
Published
May 20, 2026, 5:16 PM
Modified
Jul 23, 2026, 12:10 PM
Severity
Moderate
Public date
May 20, 2026, 2:53 PM