A flaw was found in the Keycloak REST API before version 8.0.0 where it would permit user access from a realm the user was not configured. An authenticated attacker with knowledge of a user id could use this flaw to access unauthorized information or to carry out further attacks.

It was found that Keycloak's SAML broker, versions up to 6.0.1, did not verify missing message signatures. If an attacker modifies the SAML Response and removes the <Signature> sections, the message is still accepted, and the message can be modified. An attacker could use this flaw to impersonate other users and gain access to sensitive information.

It was found that Keycloak's account console, up to 6.0.1, did not perform adequate header checks in some requests. An attacker could use this flaw to trick an authenticated user into performing operations via request from an untrusted domain.

A vulnerability was found in keycloak before 6.0.2. The X.509 authenticator supports the verification of client certificates through the CRL, where the CRL list can be obtained from the URL provided in the certificate itself (CDP) or through the separately configured path. The CRL are often available over the network through unsecured protocols ('http' or 'ldap') and hence the caller should verify the signature and possibly the certification path. Keycloak currently doesn't validate signatures on CRL, which can result in a possibility of various attacks like man-in-the-middle.

It was found that Keycloak's Node.js adapter before version 4.8.3 did not properly verify the web token received from the server in its backchannel logout . An attacker with local access could use this to construct a malicious web token setting an NBF parameter that could prevent user access indefinitely.

Keycloak up to version 6.0.0 allows the end user token (access or id token JWT) to be used as the session cookie for browser sessions for OIDC. As a result an attacker with access to service provider backend could hijack user’s browser session.

The SAML broker consumer endpoint in Keycloak before version 4.6.0.Final ignores expiration conditions on SAML assertions. An attacker can exploit this vulnerability to perform a replay attack.

keycloak before version 4.0.0.final is vulnerable to a infinite loop in session replacement. A Keycloak cluster with multiple nodes could mishandle an expired session replacement and lead to an infinite loop. A malicious authenticated user could use this flaw to achieve Denial of Service on the server.