This is a concurrency issue that can result in the wrong caller principal being returned from the session context of an EJB that is configured with a RunAs principal. In particular, the org.jboss.as.ejb3.component.EJBComponent class has an incomingRunAsIdentity field. This field is used by the org.jboss.as.ejb3.security.RunAsPrincipalInterceptor to keep track of the current identity prior to switching to a new identity created using the RunAs principal. The exploit consist that the EJBComponent#incomingRunAsIdentity field is currently just a SecurityIdentity. This means in a concurrent environment, where multiple users are repeatedly invoking an EJB that is configured with a RunAs principal, it's possible for the wrong the caller principal to be returned from EJBComponent#getCallerPrincipal. Similarly, it's also possible for EJBComponent#isCallerInRole to return the wrong value. Both of these methods rely on incomingRunAsIdentity. This vulnerability affects wildfly-ejb3 versions prior to 26.1.1.Final and 27.0.0.Alpha1.
CWE-863 - Incorrect Authorization
Authorization is a security mechanism performed by an application to grant or deny access to the requested resources by verifying the privileges of the user. When an application lacks effective authorization mechanisms, it enables unauthorized users to gain unintended privileges and illegitimate access to resources. Such a vulnerability may result in exposure of sensitive information, denial of service, arbitrary code execution, and complete system takeover.