# CVE-2026-97174: Keycloak-services: keycloak-services: ciba sub parameter injection causes attacker authentication to issue victim tokens

Status: published. Published: 2026-11-05. Updated: 2026-11-05.

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.

## Remediation

- workaround: 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. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Build of Keycloak (keycloak-services): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Build of Keycloak (rhbk/keycloak-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Single Sign-On 7 (keycloak-services): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 6.8 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-20

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-97174 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2539961 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-97174; retrieved 2026-11-05; source updated 2026-11-05

Revision: 71b099f1772947303747fcb76fe4bb7e61d019ee69346d883fbadbbc552b7a5b

Canonical: https://y2.dev/cve/CVE-2026-97174

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