A flaw was found in Keycloak in versions before 10.0.0, where it does not perform the TLS hostname verification while sending emails using the SMTP server. This flaw allows an attacker to perform a man-in-the-middle (MITM) attack.
The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Keycloak | Redhat | * | 10.0.0 (excluding) |
| Red Hat Single Sign On 7.3.8 | RedHat | * | |
| Red Hat Single Sign-On 7.3 for RHEL 6 | RedHat | rh-sso7-keycloak-0:4.8.20-1.Final_redhat_00001.1.el6sso | * |
| Red Hat Single Sign-On 7.3 for RHEL 7 | RedHat | rh-sso7-keycloak-0:4.8.20-1.Final_redhat_00001.1.el7sso | * |
| Red Hat Single Sign-On 7.3 for RHEL 8 | RedHat | rh-sso7-keycloak-0:4.8.20-1.Final_redhat_00001.1.el8sso | * |
Even if a certificate is well-formed, signed, and follows the chain of trust, it may simply be a valid certificate for a different site than the site that the product is interacting with. If the certificate’s host-specific data is not properly checked - such as the Common Name (CN) in the Subject or the Subject Alternative Name (SAN) extension of an X.509 certificate - it may be possible for a redirection or spoofing attack to allow a malicious host with a valid certificate to provide data, impersonating a trusted host. In order to ensure data integrity, the certificate must be valid and it must pertain to the site that is being accessed. Even if the product attempts to check the hostname, it is still possible to incorrectly check the hostname. For example, attackers could create a certificate with a name that begins with a trusted name followed by a NUL byte, which could cause some string-based comparisons to only examine the portion that contains the trusted name. This weakness can occur even when the product uses Certificate Pinning, if the product does not verify the hostname at the time a certificate is pinned.