CVE-2021-3827 is a medium-severity (CVSS 6.8) Improper Authentication vulnerability in org.keycloak:keycloak-saml-core. A fix is available for org.keycloak:keycloak-saml-core — see the affected versions and patch details below.
ECP SAML binding bypasses authentication flows
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-saml-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
Description
A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.keycloak:keycloak-saml-core | all versions | 18.0.0org.keycloak:keycloak-saml-core:18.0.0 |
Affected Products
keycloakredhatopenshift container platformredhatsingle sign-onredhatDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-saml-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.keycloak:keycloak-saml-core to 18.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3827 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.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Single Sign-On 7.5 for RHEL 7 | rh-sso7-keycloak-0:15.0.4-1.redhat_00001.1.el7sso | RHSA-2022:0151 |
| Red Hat Single Sign-On 7.5 for RHEL 8 | rh-sso7-keycloak-0:15.0.4-1.redhat_00001.1.el8sso | RHSA-2022:0152 |
| RHEL-8 based Middleware Containers | rh-sso-7/sso75-openshift-rhel8:7.5-15 | RHSA-2022:0164 |
| RHSSO 7.5.1 | keycloak-server-spi-private | RHSA-2022:0155 |
Frequently Asked Questions
Is CVE-2021-3827 in your dependencies?
Find it across Maven, including transitive dependencies.