CVE-2026-19607

MEDIUM 5.3

Keycloak-services: keycloak-services: broker-originated username collision causes account lockout

CVSS Score

5.3

EPSS Score

0.0%

EPSS Percentile

0th

A flaw was found in the first-broker-login flow of the keycloak-services component. This component handles the initial authentication and account linking when a user logs in via an external identity provider. The issue allows an attacker to register a matching username on an external provider to trigger a collision in Keycloak, which results in the legitimate user being locked out of their account.

CWE	CWE-287
Vendor	red hat
Product	red hat build of keycloak 26.4
Published	Sep 16, 2026
Last Updated	Sep 16, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Affected Versions

Red Hat / Red Hat build of Keycloak 26.4

All versions affected

Red Hat / Red Hat build of Keycloak 26.4

All versions affected

Red Hat / Red Hat build of Keycloak 26.4

All versions affected

Red Hat / Red Hat build of Keycloak 26.4.16

All versions affected

Red Hat / Red Hat build of Keycloak 26.4.16

All versions affected

Red Hat / Red Hat build of Keycloak 26.6

All versions affected

Red Hat / Red Hat build of Keycloak 26.6

All versions affected

Red Hat / Red Hat build of Keycloak 26.6

All versions affected

Red Hat / Red Hat build of Keycloak 26.6.7

All versions affected

Red Hat / Red Hat build of Keycloak 26.6.7

All versions affected

Red Hat / Red Hat Single Sign-On 7

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

access.redhat.com: https://access.redhat.com/errata/RHSA-2026:68276 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:68277 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:68278 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:68280 access.redhat.com: https://access.redhat.com/security/cve/CVE-2026-19607 bugzilla.redhat.com: https://bugzilla.redhat.com/show_bug.cgi?id=2514529

Credits

Red Hat would like to thank Anurag Mondal (NetSPI) for reporting this issue.