[Security-announce][CVE-2026-2297] SourcelessFileLoader does not use io.open_code()

There is a MEDIUM severity vulnerability affecting CPython.

The import hook in CPython that handles legacy *.pyc files (SourcelessFileLoader) is incorrectly handled in FileLoader (a base class) and so does not use io.open_code() to read the .pyc files. sys.audit handlers for this audit event therefore do not fire.

Please see the linked CVE ID for the latest information on affected versions:

• https://www.cve.org/CVERecord?id=CVE-2026-2297

• https://github.com/python/cpython/pull/145507