In this paper, we present a novel ciphertext-policy attribute based encryption (CP-ABE) scheme that offers a flexible access structure. Our proposed scheme incorporates an access tree as its access control policy, enabling fine-grained access control over encrypted data. The security of our scheme is provable under the hardness assumption of the decisional Ring-Learning with Errors (R-LWE) problem, ensuring robust protection against unauthorized access. CP-ABE is a cryptographic technique that allows data owners to encrypt their data with access policies defined in terms of attributes. Only users possessing the required attributes can decrypt and access the encrypted data. Our scheme extends the capabilities of CP-ABE by introducing a flexible access structure based on an access tree. This structure enables more complex and customizable access policies, accommodating a wider range of real-world scenarios. To ensure the security of our scheme, we rely on the decisional R-LWE problem, a well-established hardness assumption in cryptography. By proving the security of our scheme under this assumption, we provide a strong guarantee of protection against potential attacks. Furthermore, our proposed scheme operates in the standard model, which means it does not rely on any additional assumptions or idealized cryptographic primitives. This enhances the practicality and applicability of our scheme, making it suitable for real-world deployment. We evaluate the performance and efficiency of our scheme through extensive simulations and comparisons with existing CP-ABE schemes. The results demonstrate the effectiveness and scalability of our proposed approach, highlighting its potential for secure and flexible data access control in various domains.