MONAI prior to version 1.6.1 includes a flaw in the check_hash function where the function silently returns true when the supplied hash value is null. The default hash type is MD5, which is insecure, and the function does not properly validate the integrity of downloaded bundles, datasets, or model archives. An attacker who can perform a man‑in‑the‑middle attack or compromise a registry can replace legitimate files with malicious ones, causing the system to accept them without detection. The potential consequence is that arbitrary code can be executed in the context of the MONAI application, leading to full system compromise. The weakness is a classic example of insufficient cryptographic protection (CWE‑327).

Project‑MONAI’s MONAI library, versions before 1.6.1, is affected. The vulnerability results from the check_hash implementation in this library and applies to any deployment that uses the default MD5 hash without explicit validation.

The CVSS score of 8.2 indicates a high severity level. EPSS data is unavailable, and the vulnerability is not listed in the CISA KEV catalog. Attackers can exploit the weakness over a network connection (e.g., a man‑in‑the‑middle scenario) or by compromising a registry that hosts MONAI packages. The risk is that any system that relies on undisturbed downloads from the default sources could be affected, potentially leading to remote code execution. The vulnerability can be exploited with low effort if the attacker can influence the download process or supply a bundle without hashes, resulting in the silent acceptance of malicious content.