CVE-2020-27838 is a medium-severity (CVSS 6.5) Improper Authentication vulnerability in org.keycloak:keycloak-core. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for org.keycloak:keycloak-core — see the affected versions and patch details below.
Keycloak discloses information without authentication
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-coreReal-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 in versions prior to 13.0.0. The client registration endpoint allows fetching information about PUBLIC clients (like client secret) without authentication which could be an issue if the same PUBLIC client changed to CONFIDENTIAL later. The highest threat from this vulnerability is to data confidentiality.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.keycloak:keycloak-core | all versions | 13.0.0org.keycloak:keycloak-core:13.0.0 |
Affected Products
keycloakredhatsingle sign-onredhatResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.keycloak:keycloak-core to 13.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-27838 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
How to detect CVE-2020-27838
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2020-27838 -u https://target- Template
- KeyCloak - Information Exposure
- Severity
- medium
- Impact
- The vulnerability allows an attacker to gain sensitive information from the KeyCloak server.
- Remediation
- Apply the latest security patches or updates provided by the KeyCloak vendor.
Template by ProjectDiscovery nuclei-templates (mchklt), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2020-27838 in your dependencies?
Find it across Maven, including transitive dependencies.