Flask-Reuploaded vulnerable to Remote Code Execution via Server-Side Template Injection

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-27641: 1.34% estimated exploitation activity in the next 30 days; percentile 71.26 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 ```python 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…

Published by the source

25 Feb 2026, 19:06 UTC

Last modified by the source

27 Oct 2026, 17:00 UTC

Source last checked

28 Oct 2026, 06:05 UTC

1. Revision 5 · amended · 28 Oct 2026

   Amended from osv record GHSA-65mp-fq8v-56jr

2. Revision 4 · amended · 27 Oct 2026

   Amended from ghsa record GHSA-65mp-fq8v-56jr

3. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-65mp-fq8v-56jr

4. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-65mp-fq8v-56jr

5. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-65mp-fq8v-56jr

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# Patch Next advisory brief: CVE-2026-27641

Advisory: Flask-Reuploaded vulnerable to Remote Code Execution via Server-Side Template Injection
IDs: CVE-2026-27641, GHSA-65mp-fq8v-56jr
Record: https://patchnext.com/advisories/cve-2026-27641 (revision 5, source checked 28 Oct 2026, 06:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flask-reuploaded 1.5.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flask-reuploaded: affected < 1.5.0; fixed in 1.5.0

## Suggested inspection (read-only)
- `python -m pip show flask-reuploaded`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flask-reuploaded.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-65mp-fq8v-56jr (GitHub-reviewed advisory GHSA-65mp-fq8v-56jr lists affected ranges: PyPI flask-reuploaded >=0 <1.5.0)
- Verified: https://osv.dev/vulnerability/GHSA-65mp-fq8v-56jr (OSV record GHSA-65mp-fq8v-56jr lists affected ranges: PyPI flask-reuploaded >=0 <1.5.0 (fixed))

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