CVE-2026-4633: Keycloak: keycloak: user enumeration via differential error messages

Severity: low (CVSS 3.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-23 · updated 2026-10-22
Weakness: CWE-209

Description

A flaw was found in Keycloak. A remote attacker can exploit differential error messages during the identity-first login flow when Organizations are enabled. This vulnerability allows an attacker to determine the existence of users, leading to information disclosure through user enumeration.

Affected products

Red Hat build of Keycloak 26.4: all versions

References

https://access.redhat.com/errata/RHSA-2026:19596
https://access.redhat.com/security/cve/CVE-2026-4633
https://bugzilla.redhat.com/show_bug.cgi?id=2450247

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