---
id: CVE-2026-97174
title: >-
  Keycloak-services: keycloak-services: ciba sub parameter injection causes
  attacker authentication to issue victim tokens
summary: >-
  A flaw was found in the Client-Initiated Backchannel Authentication (CIBA)
  implementation of Keycloak. The CIBA endpoint fails to properly validate the
  sub parameter, allowing it to be stored as an additional request parameter.
  During th…
severity: medium
cvss: 6.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N'
cvssSource: cna
cwe:
  - CWE-20
vendor: Red Hat
product: keycloak-services
affected:
  - keycloak-services (all versions)
  - rhbk/keycloak-rhel9 (all versions)
  - keycloak-services
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-11-05T20:58:27.807112Z'
published: '2026-11-05'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:58:34.387Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-97174'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-97174'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2539961'
    label: RHBZ#2539961
tags:
  - cve.org
ingestedAt: '2026-11-05T22:38:31.937Z'
---

## Overview

A flaw was found in the Client-Initiated Backchannel Authentication (CIBA) implementation of Keycloak. The CIBA endpoint fails to properly validate the sub parameter, allowing it to be stored as an additional request parameter. During the token issuance process, this injected value overwrites the legitimate subject identifier. This allows an attacker to authenticate as themselves but receive security tokens belonging to a different victim user, leading to unauthorized account access.

## Affected

- `keycloak-services (all versions)`
- `rhbk/keycloak-rhel9 (all versions)`
- `keycloak-services`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### Workarounds

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.