Mistune: Arbitrary File Read via Include directive path traversal
Summary
A path traversal issue exists in mistune's Include directive when markdown files are processed using md.read(). A crafted include path can cause files outside the intended markdown directory to be accessed.
Details
The issue occurs in the Include.parse() method where user-supplied paths are joined and normalized without verifying that the resulting path remains within an expected directory.
relpath = self.parse_title(m)
dest = os.path.join(os.path.dirname(source_file), relpath)
dest = os.path.normpath(dest)Because the final path is not restricted to a trusted base directory, path traversal sequences such as ../ may reference files outside the intended location.
Proof of Concept
Create a markdown file:
.. include:: ../../../example.txtProcess it using:
import mistune
from mistune.directives import RSTDirective, Include
md = mistune.create_markdown(
plugins=[RSTDirective([Include()])]
)
result, state = md.read("test.md")
print(result)Impact
Applications that process untrusted markdown files with the Include directive enabled may allow unintended file access. The impact depends on how the feature is used and what files are accessible to the running process.
Recommended Fix
Validate the resolved path and ensure it remains within an allowed directory before opening the file.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | mistune | < 3.3.0 | 3.3.0 |
References
- https://github.com/lepture/mistune/releases/tag/v3.3.0
- https://github.com/lepture/mistune/commit/1bef343ade163fc3bb95572b15be720084cdb993
- https://github.com/lepture/mistune/security/advisories/GHSA-r4rv-85jg-w4mf
- https://nvd.nist.gov/vuln/detail/CVE-2026-59924
- https://github.com/lepture/mistune
- https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2212.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N- Weakness (CWE)
CWE-22- Platform
- Python (PyPI)
- Package
mistune- Disclosed
- 08.07.2026
- Updated
- 11.10.2026 14:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2212 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-r4rv-85jg-w4mf - CC BY 4.0
Vulnerability history: mistune
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 20
- First → latest
- 10.2017 09.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- High 7
- Medium 13
Disclosures per year
- 2017: 2
- 2018: 0
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 1
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 17
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