Python-Multipart has Arbitrary File Write via Non-Default Configuration

Exploitation

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

CVSS

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

EPSS

• CVE-2026-24486: 2.21% estimated exploitation activity in the next 30 days; percentile 82.59 (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.

Summary A Path Traversal vulnerability exists when using non-default configuration options UPLOADDIR and UPLOADKEEPFILENAME=True. An attacker can write uploaded files to arbitrary locations on the filesystem by crafting a malicious filename. Details When UPLOADDIR is set and UPLOADKEEPFILENAME is True, the library constructs the file path using os.path.join(filedir, fname). Due to the behavior of os.path.join(), if the filename begins with a /, all preceding path components are discarded: This allows an attacker to bypass the intended upload directory and write files to arbitrary paths. Affected Configuration Projects are only affected if all of the following are true: - UPLOADDIR is set - UPLOADKEEPFILENAME is set to True - The uploaded file exceeds MAXMEMORYFILESIZE (triggering a flush to disk) The default configuration is not vulnerable. Impact Arbitrary file write to attacker-controlled paths on the filesystem. Mitigation Upgrade to version 0.0.22, or avoid using…

Published by the source

26 Jan 2026, 23:28 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wp53-j4wj-2cfg

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-wp53-j4wj-2cfg

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# Patch Next advisory brief: CVE-2026-24486

Advisory: Python-Multipart has Arbitrary File Write via Non-Default Configuration
IDs: CVE-2026-24486, GHSA-wp53-j4wj-2cfg
Record: https://patchnext.com/advisories/cve-2026-24486 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: python-multipart 0.0.22. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI python-multipart: affected < 0.0.22; fixed in 0.0.22

## Suggested inspection (read-only)
- `python -m pip show python-multipart`: 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 python-multipart.
- 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://osv.dev/vulnerability/GHSA-wp53-j4wj-2cfg (OSV record GHSA-wp53-j4wj-2cfg lists affected ranges: PyPI python-multipart >=0 <0.0.22 (fixed))
- Verified: https://github.com/advisories/GHSA-wp53-j4wj-2cfg (GitHub-reviewed advisory GHSA-wp53-j4wj-2cfg lists affected ranges: PyPI python-multipart >=0 <0.0.22)

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