Description
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.
References9
- github.com/python/cpython/commit/482d6f8bdba9da3725d272e8bb4a2d…
- github.com/python/cpython/commit/69ddd9bb2cc4bd69b1565647c18659…
- github.com/python/cpython/commit/876858c9f65d9ab656c7fa639f268c…
- github.com/python/cpython/commit/a51b1b512de1d56b3714b65628a2ea…
- github.com/python/cpython/commit/c70adad78caeeea33f92f560ecb933…
- github.com/python/cpython/commit/e58e9802b9bec5cdbf48fc9bf1da5f…
- github.com/python/cpython/issues/145506
- github.com/python/cpython/pull/145507
- www.openwall.com/lists/oss-security/2026/03/05/6
Metrics
- CVSS 4.0
-
5.7
MEDIUM
Score source: CNA
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 13 · as of 12 November 2026
- CWE
- CWE-668
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.