There is a defect in the CPython standard library module “mimetypes” where on Windows the default list of known file locations are writable meaning other users can create invalid files to cause MemoryError to be raised on Python runtime startup or have file extensions be interpreted as the incorrect file type.
This defect is caused by the default locations of Linux and macOS platforms (such as “/etc/mime.types”) also being used on Windows, where they are user-writable locations (“C:etcmime.types”).
To work-around this issue a user can call mimetypes.init() with an empty list (“[]”) on Windows platforms to avoid using the default list of known file locations.
The product searches for critical resources using an externally-supplied search path that can point to resources that are not under the product’s direct control.
This might allow attackers to execute their own programs, access unauthorized data files, or modify configuration in unexpected ways. If the product uses a search path to locate critical resources such as programs, then an attacker could modify that search path to point to a malicious program, which the targeted product would then execute. The problem extends to any type of critical resource that the product trusts. Some of the most common variants of untrusted search path are: