CVE-2026-9087
Analyzed Analyzed - Analysis Complete
Keycloak Session Linking Vulnerability via IdP Identity Confusion

Publication date: 2026-05-20

Last updated on: 2026-06-02

Assigner: Red Hat, Inc.

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.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-05-20
Last Modified
2026-06-02
Generated
2026-06-10
AI Q&A
2026-05-20
EPSS Evaluated
2026-06-08
NVD
CVE-2026-9087
EUVD
EUVD-2026-31134
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
redhat build_of_keycloak *
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-639 The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability exists in Keycloak's cross-session email verification process. The verification proof is keyed only by the local user ID and the identity provider alias, but it is not bound to the specific upstream identity that was actually verified.

As a result, a second upstream account from the same identity provider can misuse this verification proof to link itself to the victim's local account.

Impact Analysis

This vulnerability can lead to unauthorized linking of accounts. An attacker controlling a second upstream account on the same identity provider can consume the verification proof intended for another user and link their account to the victim's local account.

This could result in unauthorized access or actions performed under the victim's local account, potentially compromising confidentiality and integrity of the victim's data.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-9087. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart