# CVE-2026-19607: Keycloak first-broker-login account collision flaw

Source: https://junglewise.ai/threats/cve-2026-19607-keycloak-first-broker-login-account-collision-flaw  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-19607 · Severity: medium · CVSS 5.3 · Published 2026-09-16

Keycloak is an open-source identity and access management system used to authenticate users and manage access to applications. A flaw in its external identity provider login flow allows an attacker to register a matching username on an external provider to cause a username collision, locking legitimate users out of their Keycloak accounts.

Technologies: [Keycloak](https://junglewise.ai/threats/technologies/keycloak). Vendors: [Keycloak](https://junglewise.ai/threats/vendors/keycloak).

## Quick answers

**Is CVE-2026-19607 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19607 being exploited in the wild.

**How severe is CVE-2026-19607?** Medium severity, with a CVSS score of 5.3, published 16 September 2026.

**Which products and versions are affected?** Keycloak <UNKNOWN>.

**Is there a fix for CVE-2026-19607?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-19607 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-19607?** Check whether you run Keycloak at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in the first-broker-login flow of the keycloak-services component, which handles initial authentication and account linking for users logging in via external identity providers. An attacker can exploit this by registering a matching username on an external provider to trigger a username collision in Keycloak. The attack results in denial of service to the legitimate user, as they become locked out of their account. The vulnerability requires network access to an affected Keycloak instance and knowledge of target usernames, but does not require prior authentication. Patches are expected from the vendor.

## Affected products

- Keycloak Keycloak <UNKNOWN>

## Timeline

- 2026-09-16: disclosed

## References

- [https://catalog.redhat.com/software/containers/](https://catalog.redhat.com/software/containers/)
- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)

## Related threats

- [Keycloak login-failure storage synchronization error in MySQL/MariaDB](https://junglewise.ai/threats/cve-2026-112201-a-flaw-was-found-in-the-login-failure-storage-component-of)
- [Keycloak PKCE bypass in login after password reset](https://junglewise.ai/threats/cve-2026-125652-a-flaw-was-found-in-the-keycloak-services-component-of-keycloak)
- [Keycloak server arbitrary code execution in client authorization](https://junglewise.ai/threats/cve-2026-120984-a-flaw-was-found-in-the-keycloak-server-s-client-management)
- [Keycloak token sanitization bypass in protocol mapper](https://junglewise.ai/threats/cve-2026-97848-a-flaw-was-found-in-the-token-sanitization-logic-of-keycloak-an)
- [Keycloak Dynamic Client Registration privilege escalation](https://junglewise.ai/threats/cve-2026-96547-a-flaw-was-found-in-the-dynamic-client-registration-component-of)