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 v4.0: 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/E:U/U:Green
CVE-ID: CVE-2021-3827
CWE-ID: CWE-288
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Keycloak
Affected software:
Keycloak
Keycloak
Detailed vulnerability description
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.
How to mitigate CVE-2021-3827
Install updates from vendor's website.