<p>With the growing demand for secure image transmission, image encryption has become an active research topic in modern information security. Although numerous chaos-based image encryption schemes have been proposed, many of them still concentrate on single-image encryption (SIE) or adopt limited confusion–diffusion depth within a single encryption round. To address the issues of limited security strength and low efficiency in existing schemes, this paper proposes a novel multi-image encryption (MIE) scheme based on a hyperchaotic system and dual S-boxes, aiming to achieve higher encryption efficiency and stronger resistance to attacks. The proposed scheme comprises three main stages: cubic confusion, bidirectional diffusion, and S-box based confusion. First, the ISL-HMC hyperchaotic map is iterated to generate pseudorandom sequences, which are then used for S-box generation as well as for the confusion and diffusion processes. The large hyperchaotic range and key selection space of the selected map can be demonstrated by the bifurcation diagrams and Lyapunov exponents under different parameters. Then, the multiple original images are fused into a cube for initial confusion. The cube is respectively reshaped into a vector and two-dimensional image for bidirectional diffusion and S-box based confusion. Experimental results demonstrate that the proposed scheme achieves correct decryption, high randomness (information entropy of 7.9970), and strong resistance to statistical and differential attacks, with NPCR and UACI values of 99.6194% and 33.4695%, respectively. Overall, the proposed scheme demonstrates promising application potential in high-capacity image protection and secure communication transmission.</p>