GHSA-R4RV-85JG-W4MF

Vulnerability from github – Published: 2026-07-20 21:34 – Updated: 2026-07-20 21:34
VLAI
Summary
Mistune: Arbitrary File Read via Include directive path traversal
Details

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.

Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59924"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:34:53Z",
    "nvd_published_at": "2026-07-08T17:17:28Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nA path traversal issue exists in mistune\u0027s `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.\n\n### Details\n\nThe 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.\n\n```python\nrelpath = self.parse_title(m)\ndest = os.path.join(os.path.dirname(source_file), relpath)\ndest = os.path.normpath(dest)\n```\n\nBecause the final path is not restricted to a trusted base directory, path traversal sequences such as `../` may reference files outside the intended location.\n\n### Proof of Concept\n\nCreate a markdown file:\n\n```markdown\n.. include:: ../../../example.txt\n```\n\nProcess it using:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, Include\n\nmd = mistune.create_markdown(\n    plugins=[RSTDirective([Include()])]\n)\n\nresult, state = md.read(\"test.md\")\nprint(result)\n```\n\n### Impact\n\nApplications 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.\n\n### Recommended Fix\n\nValidate the resolved path and ensure it remains within an allowed directory before opening the file.",
  "id": "GHSA-r4rv-85jg-w4mf",
  "modified": "2026-07-20T21:34:53Z",
  "published": "2026-07-20T21:34:53Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-r4rv-85jg-w4mf"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59924"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/1bef343ade163fc3bb95572b15be720084cdb993"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2212.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune: Arbitrary File Read via Include directive path traversal"
}



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