<p>This paper presents the cryptanalysis of four recently proposed image encryption algorithms that utilize chaos-based confusion-diffusion techniques. The first algorithm follows a single round of permutation-substitution using a novel one-dimensional chaotic map for medical image encryption. The second method proposes color image encryption that follows two-stage confusion and diffusion at block and pixel levels, using multiple chaotic and hyperchaotic maps on each color plane. The third method follows pixel-bit-level-based permutation-substitution operations for grayscale image encryption. The fourth method employs a single round of cross-channel pixel permutation and block-pixel level substitution for color image encryption. All techniques have been validated for their security performance through some standard security analysis and claims of resilience against common attacks. However, careful cryptanalysis reveals common weaknesses in these techniques, making them vulnerable to attacks. The diffusion functions in all these methods use variants of XOR operations, which can be combined and reduced to linear XOR forms, allowing easy identification of equivalent diffusion keys. Similarly, the permutations in these methods, through key-dependent transpositions, scan patterns, and graycode transformations, produce fixed permutation structures across images with the same encryption key, enabling easy reconstruction of the permutation matrix. Using these observations, we employ chosen-plaintext analysis to compromise these cryptosystems and successfully decrypt and recover the secret images without knowing the original encryption key. Additionally, this paper proposes improvements in the design of chaos-based image encryption algorithms to ensure the required level of security.</p>