Authentication bypass using an alternate path or channel in Keycloak - CVE-2021-3827

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Main Vulnerability Database Vulnerabilities #VU59892

Authentication bypass using an alternate path or channel in Keycloak - CVE-2021-3827

Published: January 20, 2022 / Updated: June 29, 2026


Vulnerability identifier: #VU59892
CSH Severity: Medium
CVSS v4: 7.6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-3827
CWE-ID: CWE-288
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to bypass 2FA authentication.

The vulnerability exists due to an error in ECP SAML binding flow within keycloak-server-spi-private. A remote attacker can send SOAP request with an AuthnRequest and Authorization header with the user's credentials and bypass MFA authentication.


Affected software

Keycloak
Red Hat Single Sign-On

How to mitigate CVE-2021-3827

Install updates from vendor's website.

Keycloak - update to 18.0.0
Red Hat Single Sign-On - update to 7.5.1

External References

Related Security Bulletins