MultipartParser denial of service with too many fields or files

Exploitation

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

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2023-30798: 1.30% estimated exploitation activity in the next 30 days; percentile 70.45 (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 The MultipartParser using the package python-multipart accepts an unlimited number of multipart parts (form fields or files). Processing too many parts results in high CPU usage and high memory usage, eventually leading to an <abbr title="out of memory"OOM</abbr process kill. This can be triggered by sending too many small form fields with no content, or too many empty files. For this to take effect application code has to: Have python-multipart installed and call request.form() or via another framework like FastAPI, using form field parameters or UploadFile parameters, which in turn calls request.form(). Patches The vulnerability is solved in Starlette 0.25.0 by making the maximum fields and files customizable and with a sensible default (1000). Applications will be secure by just upgrading their Starlette version to 0.25.0 (or FastAPI to 0.92.0). If application code needs to customize the new max field and file number, there are new request.form() parameters (with the…

Published by the source

14 Feb 2023, 21:31 UTC

Last modified by the source

8 Jul 2026, 06:52 UTC

Source last checked

26 Oct 2026, 13:25 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-74m5-2c7w-9w3x

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-74m5-2c7w-9w3x

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# Patch Next advisory brief: CVE-2023-30798

Advisory: MultipartParser denial of service with too many fields or files
IDs: CVE-2023-30798, GHSA-74m5-2c7w-9w3x
Record: https://patchnext.com/advisories/cve-2023-30798 (revision 3, source checked 26 Oct 2026, 13:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: starlette 0.25.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI starlette: affected < 0.25.0; fixed in 0.25.0

## Suggested inspection (read-only)
- `python -m pip show starlette`: 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 starlette.
- 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-74m5-2c7w-9w3x (OSV record GHSA-74m5-2c7w-9w3x lists affected ranges: PyPI starlette >=0 <0.25.0 (fixed))
- Verified: https://github.com/advisories/GHSA-74m5-2c7w-9w3x (GitHub-reviewed advisory GHSA-74m5-2c7w-9w3x lists affected ranges: PyPI starlette >=0 <0.25.0)

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