GHSA-r4rv-85jg-w4mf
MEDIUMMistune: Arbitrary File Read via Include directive path traversal
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
mistuneReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.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)
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | mistune | all versions | 3.3.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mistune. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update mistune to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-r4rv-85jg-w4mf is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-r4rv-85jg-w4mf is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-r4rv-85jg-w4mf. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-r4rv-85jg-w4mf in your dependencies?
O3 detects GHSA-r4rv-85jg-w4mf across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.