PyPI · mistune
Mistune: Arbitrary File Read via Include directive path traversal
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.
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.
Create a markdown file:
.. include:: ../../../example.txt
Process 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)
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.
Validate the resolved path and ensure it remains within an allowed directory before opening the file.
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Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.