Bug 2450247 (CVE-2026-4633)

Summary: CVE-2026-4633 keycloak: Keycloak: User enumeration via differential error messages
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: aschwart, boliveir, mposolda, pjindal, rmartinc, ssilvert, sthorger, vmuzikar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
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.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-03-23 08:36:22 UTC 
User enumeration via differential error messages in Organizations +
identity-first login flow. Existing users receive "Invalid Password"
while non-existent users receive "Invalid username or password."
Requirements to exploit: Organizations enabled on realm,
identity-first login flow active, network access to login endpoint.

Steps to reproduce:

1. Create a realm and enable Organizations.
2. Create an organization and add a user with a known password.
3. Navigate to /realms/[realm]/account/.
4. Enter a non-existent username, click "Sign in," enter any password,
and submit.
5. Observe error: "Invalid username or password."
6. Repeat with an existing username.
7. Observe error: "Invalid Password."
8. The differential response confirms user existence.