Component-Based Software Engineering is a perfect approach for rapid software development with the maturity of components. The estimation of Component-Based Software (CBS) reliability from the reliabilities of constituent components and architecture is a matter of concern. In this paper we propose a Reliability Estimation Model for CBS to estimate the reliability through path propagation probability and component impact factor. This model incorporates the idea of path propagation to estimate overall system reliability after integration of components, which considers the contribution of the individual components that get activated during an execution path. This model also estimates the impact factor of individual components on overall reliability. The impact factor can be used to focus the efforts to obtain the best reliability improvements. To evaluate the Reliability Estimation Model including both the factors, we implement it through JAVA, which is based on an adapted example case study. Lastly we conclude that proposed model is useful to estimate the reliability of CBS and can be used adaptively in early stages of software development.