CVE-2026-71492: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in masci banks

In masci banks versions before 2.4.5, the DirectoryPromptRegistry.set() method in src/banks/registries/directory.py improperly handles Prompt.name and Prompt.version values by directly interpolating them into filesystem paths without validating or canonicalizing the path. This allows relative path traversal sequences (e.g., ../victim/foo) or absolute paths to escape the configured registry root directory. When overwrite=True is set, existing files can be replaced. The malicious path is persisted in index.json and reloaded later, allowing the out-of-root path to survive across registry loads. This vulnerability enables an attacker who can influence Prompt.name or Prompt.version to write arbitrary bytes to attacker-chosen writable paths on the filesystem accessible by the application process. The vulnerability is resolved in version 2.4.5.

An attacker with the ability to control Prompt.name or Prompt.version can exploit this vulnerability to write arbitrary files to locations outside the intended directory. This could lead to overwriting critical files, potentially causing denial of service or enabling further attacks depending on the application context. The vulnerability requires some level of privileges (low privileges) and partial attacker interaction, and it does not require user interaction. The CVSS 4.0 score is 6.0 (medium severity).

This vulnerability is fixed in masci banks version 2.4.5. Users should upgrade to version 2.4.5 or later to remediate this issue. No official patch link is provided in the advisory, but upgrading to the fixed version is the recommended action. Until upgrading, avoid forwarding untrusted input into Prompt.name or Prompt.version fields to mitigate exploitation risk.