CVE-2025-54121
Starlette has possible denial-of-service vector when parsing large files in multipart forms
MEDIUM 5.3
At a glance
- Source
- NVD
- EPSS
- EPSS 0.66 % · percentile 51 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Deferred
Description
Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can't accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2.
Weaknesses (CWE)
- CWE-770 — Allocation of Resources Without Limits or Throttling
References
- https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73
- https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1
- https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14
- https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | GitHub_M |
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-2c2j-9gv5-cj73 — Starlette has possible denial-of-service vector when parsing large files in multipart forms
- PYSEC-2026-1941 — Starlette has possible denial-of-service vector when parsing large files in multipart forms
European references
- ENISA EUVD · EUVD-2025-22159
- GCVE · GCVE-0-2025-54121
CERT-FR advisories
- CERTFR-2025-AVI-1057 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2025-AVI-1051 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
Affected products
| Product | Versions |
|---|---|
| encode · starlette | affected < 0.47.2 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |