CVE-2026-4633 is a low-severity (CVSS 3.7) CWE-209 vulnerability in org.keycloak:keycloak-services. A fix is available for org.keycloak:keycloak-services — see the affected versions and patch details below.
Keycloak's identity-first login flow exposes user information
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-4633.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
org.keycloak:keycloak-services☕org.keycloak:keycloak-servicesReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.keycloak:keycloak-services | ≥ 26.5.0&&< 26.6.1 | 26.6.1org.keycloak:keycloak-services:26.6.1 |
| ☕Maven | org.keycloak:keycloak-services | all versions | 26.4.12org.keycloak:keycloak-services:26.4.12 |
Affected Products
build of keycloakredhatDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-services, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.keycloak:keycloak-services to 26.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4633 is resolved across your whole dependency graph.
Workarounds
Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This flaw has a LOW impact. Keycloak is vulnerable to user enumeration due to differential error messages during the identity-first login flow. Exploitation requires Organizations to be enabled on the realm and the identity-first login flow to be active. This could lead to information disclosure by allowing an…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.Source: Red Hat security advisory for CVE-2026-4633 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-4633 in your dependencies?
Find it across Maven, including transitive dependencies.