---
id: "CVE-2026-4633"
kind: "vulnerability"
aliases: ["CVE-2026-4633", "GHSA-rhgq-f8x5-j2jc"]
title: "Keycloak's identity-first login flow exposes user information"
severity: "low"
cvss: 3.700000047683716
epss: 0.0037899999879300594
exploited: false
status: "open"
category: "package"
products: [{"name": "org.keycloak:keycloak-services", "fixed": ["26.6.1"], "affected": ">= 26.5.0, < 26.6.1", "ecosystem": "maven"}, {"name": "org.keycloak:keycloak-services", "fixed": ["26.4.12"], "affected": "< 26.4.12", "ecosystem": "maven"}, {"name": "redhat build of keycloak", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["maven", "vendor"]
tags: ["cwe-209", "identity", "java", "keycloak", "package", "self-hosted"]
not_affected_if: ["keycloak-below-26.4.0-or-patched-version", "organizations-disabled"]
published_at: "2026-03-23T11:16:25+00:00"
first_seen_at: "2026-10-23T19:11:31+00:00"
updated_at: "2026-10-23T23:44:52+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-rhgq-f8x5-j2jc", "first_seen_at": "2026-10-23T19:11:31+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4633", "first_seen_at": "2026-10-23T23:44:52+00:00"}]
---

# Keycloak's identity-first login flow exposes user information

Keycloak's identity-first login returns different error messages depending on whether a user exists, when Organizations are enabled. A remote attacker can use this to confirm which usernames or emails have accounts, enabling user enumeration.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- maven:org.keycloak:keycloak-services affected >= 26.5.0, < 26.6.1 fixed 26.6.1
- maven:org.keycloak:keycloak-services affected < 26.4.12 fixed 26.4.12
- vendor:redhat build of keycloak affected ? fixed ?

## How to check

Check whether the Organizations feature is enabled in the Keycloak realm or server configuration; the sources do not give a specific command or file.
Check the keycloak-services version in your build or deployment against the affected ranges.

## Fix

Upgrade maven:org.keycloak:keycloak-services to 26.6.1 for the 26.5.x line, or to 26.4.12 for versions below 26.4.12.

## Timeline

- 2026-10-23T19:11:31+00:00 ghsa https://github.com/advisories/GHSA-rhgq-f8x5-j2jc
- 2026-10-23T23:44:52+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-4633

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_