PYSEC-2026-341

Vulnerability from pysec - Published: 2026-06-29 11:50 - Updated: 2026-07-01 20:22
VLAI
Details

Impact

A critical path traversal and extension bypass vulnerability in Flask-Reuploaded allows remote attackers to achieve arbitrary file write and remote code execution through Server-Side Template Injection (SSTI).

Patches

Flask-Reuploaded has been patched in version 1.5.0

Workarounds

  1. Do not pass user input to the name parameter
  2. Use auto-generated filenames only
  3. Implement strict input validation if name must be used
from werkzeug.utils import secure_filename
import os

# Sanitize user input before passing to save()
 safe_name = secure_filename(request.form.get('custom_name'))
# Remove path separators
 safe_name = os.path.basename(safe_name)
# Validate extension matches policy
if not photos.extension_allowed(photos.get_extension(safe_name)):
    abort(400)

filename = photos.save(file, name=safe_name)

Resources

The fix is documented in the pull request, see https://github.com/jugmac00/flask-reuploaded/pull/180.

A proper write-up was created by the reporter of the vulnerability, Jaron Cabral (https://www.linkedin.com/in/jaron-cabral-751994357/), but is not yet available as of time of this publication.

Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impacted products
Name purl
flask-reuploaded pkg:pypi/flask-reuploaded
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "flask-reuploaded",
        "purl": "pkg:pypi/flask-reuploaded"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.3",
        "0.3.1",
        "0.3.2",
        "0.4.0",
        "0.5.0",
        "1.0.0",
        "1.1.0",
        "1.2.0",
        "1.3.0",
        "1.4.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27641",
    "GHSA-65mp-fq8v-56jr"
  ],
  "details": "### Impact\nA critical path traversal and extension bypass vulnerability in Flask-Reuploaded allows remote attackers to achieve arbitrary file write and remote code execution through Server-Side Template Injection (SSTI).\n\n### Patches\n Flask-Reuploaded has been patched in version 1.5.0\n\n### Workarounds\n\n1. **Do not pass user input to the `name` parameter**\n2. Use auto-generated filenames only\n 3. Implement strict input validation if `name` must be used\n\n```python\nfrom werkzeug.utils import secure_filename\nimport os\n\n# Sanitize user input before passing to save()\n safe_name = secure_filename(request.form.get(\u0027custom_name\u0027))\n# Remove path separators\n safe_name = os.path.basename(safe_name)\n# Validate extension matches policy\nif not photos.extension_allowed(photos.get_extension(safe_name)):\n    abort(400)\n    \nfilename = photos.save(file, name=safe_name)\n```\n\n### Resources\nThe fix is documented in the pull request, see https://github.com/jugmac00/flask-reuploaded/pull/180.\n \nA proper write-up was created by the reporter of the vulnerability, Jaron Cabral (https://www.linkedin.com/in/jaron-cabral-751994357/), but is not yet available as of time of this publication.",
  "id": "PYSEC-2026-341",
  "modified": "2026-07-01T20:22:53.047171Z",
  "published": "2026-06-29T11:50:51.002002Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-65mp-fq8v-56jr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27641"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jugmac00/flask-reuploaded/pull/180"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jugmac00/flask-reuploaded/commit/d64c6b2f71cb73734fc38baa0e3e156926361288"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jugmac00/flask-reuploaded"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/flask-reuploaded"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-65mp-fq8v-56jr"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Flask-Reuploaded vulnerable to Remote Code Execution via Server-Side Template Injection"
}


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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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